Climate Links April 2019 (updated)

Canada in a Changing Climate. Environment and Climate Change Canada.

* extra links added April 29th *

Canada says global carbon pollution must be reduced to 'near zero' to limit harsh impacts. Carl Meyer, National Observer. Apr. 1, 2019.

Canada's failure to fight climate change 'disturbing,' environment watchdog says. Mia Rabson, National Observer. Apr. 3, 2019.

'This is a wake-up call:' swift action needed on rising seas, experts say. Michael Tutton, National Observer. Apr. 8, 2019.

Last time CO2 levels were this high, there were trees at the South Pole. Damian Carrington, Guardian. Apr. 3, 2019.

Trees growing near the South Pole, sea levels 20 metres higher than now, and global temperatures 3C-4C warmer. That is the world scientists are uncovering as they look back in time to when the planet last had as much carbon dioxide in the atmosphere as it does today.

* CO2 Levels are now at a 3 million-year high. Olivia Rosane, EcoWatch. Apr. 5, 2019.

"Our results imply a strong sensitivity of the Earth system to relatively small variations in atmospheric CO2," Willeit said. "As fascinating as this is, it is also worrying."

referencing scientific research article:
* Mid-Pleistocene transition in glacial cycles explained by declining CO2 and regolith removal. Willeit et al. Science Advances. Apr. 3, 2019.


* Researchers Warn Arctic Has Entered 'Unprecedented State' That Threatens Global Climate Stability. EcoWatch. Apr. 8, 2019.

Also last month, as Common Dreams reported, the UN Environment Programme (ENUP) warned in a far-reaching report that winter temperatures in the Arctic are already "locked in" in such a way that significant sea level increases are now inevitable this century. 

Rising temperatures, along with ocean acidification, pollution, and thawing permafrost threaten the Arctic

referencing scientific research article:
* Key Indicators of Arctic climate change: 1971- 2017. Jason Box et al, IOP Science. Apr. 8, 2019.


* Permafrost collapse is accelerating carbon release. Merritt R. Turetsky et al, Nature. Apr. 30, 2019.

The sudden collapse of thawing soils in the Arctic might double the warming from greenhouse gases released from tundra

* The Blue Ocean Event and Collapsing Ecosystems. Robert Hunziker, CounterPunch. Apr. 19, 2019.

Sometime in the near future it is highly probable that the Arctic will no longer have sea ice, meaning zero ice for the first time in eons, aka: the Blue Ocean Event. 

Surely, the world is not prepared for the consequences of such an historic event, which likely turns the world topsy-turvy, negatively impacting agriculture with gonzo weather patterns, thus forcing people to either starve or fight. But, the problem may be even bigger than shortages of food, as shall be discussed....

* The transpolar drift is faltering—sea ice is now melting before it can leave the nursery. Alfred Wegener Institute, Phys.org. Apr. 3, 2019.

According to the researchers, this development not only takes the planet one step closer to an ice-free summer in the Arctic; as the sea ice dwindles, the Arctic Ocean stands to lose an important means of transporting nutrients, algae and sediments.

* Emissions from thawing Arctic permafrost may be 12 times higher than thought, scientists say. Chiara Giordano, Independent. Apr. 17, 2019.

Emissions from thawing Arctic permafrost may be 12 times higher than previously thought, scientists have discovered. 

Permafrost is a mix of soil, rock or sediment that has been frozen for at least two years which is mostly found in the uppermost areas where temperatures are rising more quickly than the rest of the world. 

When it thaws because of global warming, it releases large quantities of carbon dioxide and methane into the atmosphere, causing temperatures to rise and creating a perpetual cycle where more permafrost melts

* Protecting marine life could be key in fighting climate change as sea creatures trap and store carbon in the ocean, researcher says. Heidi Pearson, Daily Mail. Apr. 19, 2019.

• Ocean is Earth’s largest carbon sink and central element of planet’s climate cycle
• Large animals such as whales can store large quantities of carbon for long time
• Others such as otters promote kelp growth, and kelp forests store carbon
• But, expert warns no policy has been created to protect carbon storage in ocean

As the prospect of catastrophic effects from climate change becomes increasingly likely, a search is on for innovative ways to reduce the risks.  

One potentially powerful and low-cost strategy is to recognize and protect natural carbon sinks – places and processes that store carbon, keeping it out of Earth’s atmosphere. Forests and wetlands can capture and store large quantities of carbon. These ecosystems are included in climate change adaptation and mitigation strategies that 28 countries have pledged to adopt to fulfill the Paris Climate Agreement. So far, however, no such policy has been created to protect carbon storage in the ocean, which is Earth’s largest carbon sink and a central element of our planet’s climate cycle.

* ‘Death by a thousand cuts’: vast expanse of rainforest lost in 2018. Damian Carrington, Guardian. Apr. 25, 2019.

Millions of hectares of pristine tropical rainforest were destroyed in 2018, according to satellite analysis, with beef, chocolate and palm oil among the main causes. 

The forests store huge amounts of carbon and are teeming with wildlife, making their protection critical to stopping runaway climate change and halting a sixth mass extinction. But deforestation is still on an upward trend, the researchers said. 

* Climate change being fuelled by soil damage - report. Roger Harrabin, BBC. Apr. 29, 2019.

There's three times more carbon in the soil than in the atmosphere – but that carbon's being released by deforestation and poor farming. 

This is fueling climate change – and compromising our attempts to feed a growing world population, the authors will say. 

Problems include soils being eroded, compacted by machinery, built over, or harmed by over-watering. 

Hurting the soil affects the climate in two ways: it compromises the growth of plants taking in carbon from the atmosphere, and it releases soil carbon previously stored by worms taking leaf matter underground. 

The warning will come from the awkwardly-named IPBES – the Intergovernmental Science-Policy Platform on Biodiversity and Ecosystem Services - a panel studying the benefits of nature to humans.

... 

"The thin layer of soil covering the Earth's surface represents the difference between survival and extinction for most terrestrial life. "Only 3% of the planet's surface is suitable for arable production and 75 billion tonnes of fertile soil is lost to land degradation every year."

* Up to a million species face extinction, many within decades, according to the draft UN report. Marlowe Hood, AFP. Apr. 29, 2019.


* 'Catastrophic' decline threatening the Earth. Stephanie Bedo, NZHerald. Apr. 21, 2019.

A global scientific review of insect decline has warned insects will "go down the path of extinction" in a few decades, with "catastrophic" repercussions for the planet's ecosystems. The biodiversity crisis is said to be even deeper than that of climate change.

* Rapidly declining remarkability of temperature anomalies may obscure public perception of climate change. Frances Moore et al, PNAS. March 12, 2019.

Climate change exposes people to conditions that are historically unusual but that will become increasingly common over time. What kind of weather do people think of as normal or unusual under these changing conditions? We use the volume of social media posts about weather to measure the remarkability of different temperatures and show that remarkability changes rapidly with repeated exposure to unusual temperatures. The reference point for normal conditions appears to be based on weather experienced between 2 and 8 y ago. This rapidly shifting normal baseline means warming noticed by the general public may not be clearly distinguishable from zero over the 21st century, with potential implications for both the acceptance of global warming and public pressure for mitigation policies.

* The Problem With Putting A Price on the End of the World. David Leonhardt, NYT Mag. April 9, 2019.

Economists [think they] have workable policy ideas for addressing climate change. But what if they’re politically impossible?

... 

“We have a climate problem,” Nordhaus said, “because markets fail, and fail badly, in the energy sector.” The only solution, he argued, was for governments to raise the price of emissions.

* The insanity of global trade. Roar. March 30, 2019.


* Global Climate Coalition: Documents Reveal How Secretive Fossil Fuel Lobby Group Manipulated UN Climate Programs. Matt Hope via naked capitalism. Apr. 25, 2019.

A fossil fuel–backed industry group was able to influence the process behind the United Nations climate assessments for decades, using lobbyists and industry-funded scientists to manipulate international negotiations, a cache of recently discovered documents reveals.

* A Future Without Fossil Fuels? Bill McKibben, NYRB. April 4, 2019.

2020 Vision: Why You Should See the Fossil Fuel Peak Coming: a report by Kingsmill Bond (41 pp., September 2018) 

A New World: The Geopolitics of the Energy Transformation: a report by the Global Commission on the Geopolitics of Energy Transformation (88 pp., January 2019)

REVEALED: The five ways the human race could be WIPED OUT because of global warming. Rod Ardehali, Daily Mail. Apr. 10, 2019.

• The deadly possible effects of global warming have been laid bare in a new book that reveals how disease, starvation and rising tides could kill off human beings 
• 'FALTER: Has the Human Game Begun to Play Itself Out?' lists the lethal, and unexpected, ways that humans could become extinct - within a few generations
• Melting ice caps could bring back disease locked in permafrost - killing swathes 
• Natural disasters could be triggered by collapsing ice caps - with 65ft waves wiping out any coastal life in its path - repeating what happened 8,000 years ago
• Cereal crops - the cornerstone of human sustenance - could dry out because of global warming with plants unable to grow in parched new lands
• Author Bill McKibben's doomsday book asks whether we are already too late 

* Climate research needs to change to help communities plan for the future. Robert Kopp, The Conversation. April 5, 2019.

This reality means society needs to think about climate change in different ways than the past, by focusing on reducing the risk of negative effects. And speaking as a climate scientist, I recognize that climate science research, too, has to change. 

Historically, climate science has been primarily curiosity-driven – scientists seeking fundamental understanding of the way our planet works because of the inherent interest in the problem. 

Now it’s time for the climate science research enterprise to adopt an expanded approach, one that focuses heavily on integrating fundamental science inquiry with risk management.

Looking past the horizon of 2100. Sonja van Jenssen, Nature Climate Change. Apr. 26, 2019.

Long-term climate dynamics and impacts from sea level rise to heat stress make the case for much stronger mitigation efforts today

* 'Flight shame' has Swedes rethinking air travel. Johannes Ledel, Phys.org. Apr. 10, 2019.


This book ranks the top 100 solutions to climate change. The results are surprising. David Roberts, vox. Apr. 22, 2019.

A chat with Paul Hawken about his ambitious effort to “map, measure, and model” global warming solutions.

Views of Jason Box

Jason Box: April 17, 2017.

... climate change is a defining issue of our time, whether or not one accepts what science tells us. And unfortunately, the US is now confounded from Washington DC by a brand of deeply cynical politics that threatens our species tackling climate change soon enough. Historically, the largest source of climate changing pollution, the US and DC is turning its back on the Paris Agreement, a global treaty enforcing the ambition to keep climate warming under +1.5 C above pre-industrial. Our species is acting late on this crisis. Already today at +1C above pre-industrial, we’re beginning to see profound damaging effects including increased storm severity, the drying of continental interiors, and melting ice sheets.

All of these climate change effects have overall strongly negative impacts, primarily on reducing food and water security for humans and nature that surrounds.At this stage, by supporting dirty energy from projects like the Keystone XL and Dakota Access pipelines, against the will of the majority of people and treaties signed with indigenous first nations peoples, it’s clear US climate denial is a result of a bought-out political system and a fossil fuel dominated economy. US republicans and some democrats are choosing more expensive climate destabilizing energy over cleaner and safer energy systems that benefit people and nature long term. 

The most profitable industry in history, rather than using their capital and technical capacity to transition itself to become sustainable energy, its leaders like Exxon have chosen an anti-science, greedy, and reckless path. 

Fortunately, and despite obfuscation from fossil fuel corporations, fossil energy is clearly emerging as yesterday’s energy. Still, clean energy couldn’t be coming on soon enough given that carbon emissions and concentrations are already so high that we’re losing the ice sheets and harming our oceans through carbonic acidification. Our species needs to find a way to maintain a steep fall rate for carbon emissions for the foreseeable future and engage in what has been largely a missing conversation and action of turning emissions negative until we stabilize somewhere below 350 parts per million CO2. We’re currently more than 40% above pre-industrial CO2. We thus need not only to cut carbon emissions but drawdown many Giga tons carbon from the atmosphere. While an enormous task, it’s possible and urgent to avoid a Mad Max future.

North Pole overheating. Dec. 25, 2016.

The combination of 1.) extra ocean to atmosphere heat transfer enabled by record low sea ice and 2.) pulses of warm air from the south has produced stunning large temperature departures from normal.

... alarmed we’re in uncharted climate territory driven by abrupt human-driven climate change

Box: July 29, 2014.

If even a small fraction of Arctic sea floor carbon is released to the atmosphere, we're f'd.

more here:
If We Release a Small Fraction of Arctic Carbon, 'We're F'd': Climatologist.  via Motherboard. Aug. 1, 2014.

Feature Reference Articles #11

Top Climate Scientist: Humans Will Go Extinct if We Don’t Fix Climate Change by 2023. Scot Alden, GritPost. Feb. 19, 2018.

A top climate scientist is warning that climate change will wipe out all of humanity unless we stop using fossil fuels over the next five years.

In a recent speech at the University of Chicago, James Anderson — a professor of atmospheric chemistry at Harvard University — warned that climate change is drastically pushing Earth back to the Eocene Epoch from 33 million BCE, when there was no ice on either pole. Anderson says current pollution levels have already catastrophically depleted atmospheric ozone levels, which absorb 98 percent of ultraviolet rays, to levels not seen in 12 million years.

...

While some governments have made commitments to reduce carbon emissions (Germany has pledged to cut 95 percent of carbon emissions by 2050), Anderson warned that those measures were insufficient to stop the extinction of humanity by way of a rapidly changing climate. Instead, Anderson is calling for a Marshall Plan-style endeavor in which all of the world takes extreme measures to transition off of fossil fuels completely within the next five years.

Recovery is all but impossible, he argued, without a World War II-style transformation of industry—an acceleration of the effort to halt carbon pollution and remove it from the atmosphere, and a new effort to reflect sunlight away from the earth’s poles.

This has to be done, Anderson added, within the next five years.

“The chance that there will be any permanent ice left in the Arctic after 2022 is essentially zero,” Anderson said, with 75 to 80 percent of permanent ice having melted already in the last 35 years.

Carbon Pollution Has Shoved The Climate Back At Least 12 Million Years. Harvard Scientist Says. Jeff McMahon, Forbes. Jan. 15, 2018.

The level of carbon now in the atmosphere hasn't been seen in 12 million years, a Harvard scientist said in Chicago Thursday, and this pollution is rapidly pushing the climate back to its state in the Eocene Epoch, more than 33 million years ago, when there was no ice on either pole. 

"We have exquisite information about what that state is, because we have a paleo record going back millions of years, when the earth had no ice at either pole. There was almost no temperature difference between the equator and the pole," said James Anderson, a Harvard University professor of atmospheric chemistry best known for establishing that chlorofluorocarbons were damaging the Ozone Layer. 

"The ocean was running almost 10ºC warmer all the way to the bottom than it is today," Anderson said of this once-and-future climate, "and the amount of water vapor in the atmosphere would have meant that storm systems would be violent in the extreme, because water vapor, which is an exponential function of water temperature, is the gasoline that fuels the frequency and intensity of storm systems." 

People have the misapprehension that we can recover from this state just by reducing carbon emissions, Anderson said in an appearance at the University of Chicago.  

Recovery is all but impossible, he argued, without a World War II-style transformation of industry—an acceleration of the effort to halt carbon pollution and remove it from the atmosphere, and a new effort to reflect sunlight away from the earth's poles. 

This has do be done, Anderson added, within the next five years.

"The chance that there will be any permanent ice left in the Arctic after 2022 is essentially zero," Anderson said, with 75 to 80 percent of permanent ice having melted already in the last 35 years. 

"Can we lose 75-80 percent of permanent ice and recover? The answer is no." 

The answer is no in part because of what scientists call feedbacks, some of the ways the earth responds to warming. Among those feedbacks is the release of methane currently trapped in permafrost and under the sea, which will exacerbate warming. Another is the pending collapse of the Greenland ice sheet, which Anderson said will raise sea level by 7 meters (about 23 feet). 

"People at this point haven't come to grips with the irreversibility of this sea-level rise problem," Anderson said. 

... 

In Chicago Thursday, he prosecuted a moral argument that implicates university administrators who refuse to divest from fossil fuels, journalists who fail to fact-check false statements made by political candidates, and executives of fossil fuel companies who continue to pursue activities that are exacerbating climate change—especially those who mislead the public about those effects. 

"I don't understand how these people sit down to dinner with their kids,"

Making Things Clearer: Exaggeration, Jumping the Gun, and The Venus Syndrome. James Hansen. 15 Apr. 15, 2013.

I “retired” so that I can focus my time better on (1) climate science, (2) communications thereof, and (3) policy implications. I will do this via research published in the scientific literature and translations for a wider audience.

I have had the good fortune of my research being reported by top science writers: Walter Sullivan on the first major climate paper that my colleagues and I published (1), Richard Kerr (2) on my congressional testimony in the late 1980s, and Justin Gillis (3) on my retirement. Their articles raised some issues and queries, which are relevant to the task of getting the public to understand the urgency of effective policy actions.

 

1. Exaggeration? 

I have been told of specific well-respected people who have asserted that “Jim Hansen exaggerates” the magnitude and imminence of the climate threat. If only that were true, I would be happy. 

“Magnitude and imminence” compose most of the climate story. 

Magnitude. CO2, the dominant climate forcing on the long run, will stay in the climate system for millennia. The magnitude of the eventual climate response to increasing CO2 depends especially on climate sensitivity. Our best evaluation of climate sensitivity comes from Earth’s paleoclimate history, via comparisons of periods with differing climate forcings.{a} 

Unfortunately, paleoclimate data show that our early estimates of climate sensitivity were not an exaggeration. This is made clear in a paper (4) in press at the Philosophical Transactions of the Royal Society (world’s oldest scientific journal). The journal issue containing our paper will not appear until this summer. However, the publishers have allowed us to make available a nearly final version of the paper on the arXiv website for preprints. 

This paper concludes, among other things, that climate sensitivity is in the upper half of the range that has usually been estimated. Furthermore, slow feedbacks, such as change of ice sheet size and methane emissions, make the sensitivity still higher. 

Before the paper is published we will write a summary for a broader audience. 

Imminence. Recently a smart young person told me that she tends to discount global warming as a concern, because of prior assertions that we only had 5 years or 10 years before disastrous consequences — and her observation that not much has changed in the past 5 years. 

That exposes another communications problem. Scientists did not expect sea level rise of meters or “a different planet” in 5 or 10 or 20 years. In 2005 (AGU meeting) I noted that we needed to get on a different global emissions path, with decreasing emissions, within 10 years — not because dramatic climate change would occur in 10 years, but because otherwise we will build into the climate system future changes that will be out of our control. 

Climate effects are occurring already and are generally consistent with expectations. The perceptive person should notice that the climate dice are now loaded. However, changes so far a are small compared with what will happen if we are so foolish as to continue down the path of extracting and burning every fossil fuel we can find. See below. 

2. Jumping the Gun 

It has been said that I reach conclusions before the evidence warrants them. Two examples suffice to illustrate the predicament that we face. 

Late 1980s. Dick Kerr colorfully titled a 5-day scientific meeting after my 1988/89 congressional testimonies as “Hansen vs. the World on the Greenhouse Threat”{2}. Yet one of the participants told him “if there were a secret ballot at this meeting on the question, most people would say the greenhouse warming is probably there.” 

Scientific conclusions are based on integration of multiple sources of information: climate changes observed today, Earth’s history, basic theory, models, etc. Interpretation inherently involves assumptions and subjectivity, yet valid conclusions are possible.

Communication of developing science might be affected by the phenomenon of scientific reticence.{5} In the 1980s I could shrug off criticism with “It’s just a logical, well-reasoned conclusion that the greenhouse is here now,”{2} go back to research, and let nature clarify matters. 

Today it is different. The science is much clearer. And we are running out of time. 

Today. I was recently at a meeting that included many of the top researchers in climate change. There was universal agreement about the urgency of the climate crisis.

Certainty of our predicament follows from basic considerations including: (1) huge inertia and thus slow response of key parts of the climate system, especially the ocean and ice sheets, and improving observations by Argo floats and gravity satellites that confirm trends and the existence of further change in the pipeline, (2) long lifetime of any ocean warming that is allowed to occur, (3) millennial time scale that fossil fuel CO2 will stay in the climate system, (4) paleoclimate confirmation of the magnitude of the eventual climate response to large CO2 increase. 

These scientists, people who know what they are talking about, were not concerned about jumping the gun, but rather about whether the race might already be over. So they were considering the potential for air capture of CO2, in effect geo-engineering to counteract our unintended geo-engineering. 

What’s wrong with this picture? We can pass from “jumping the gun” to unavoidable deleterious consequences without passing through demands for common sense policy actions? Let’s come back to this matter after “The Venus Syndrome”. 

3. The Venus Syndrome 

I get questions from the public about the Venus Syndrome: is there a danger of “runaway” greenhouse warming on Earth leading to Venus-like conditions? Related questions concern specific positive (amplifying) feedbacks such as methane hydrates: as warming thaws tundra and destabilizes methane hydrates on continental shelves, thus releasing methane, won’t this cause more warming, thus more methane release, thus more warming — a runaway warming? 

Amplifying feedbacks. Let’s consider a positive climate forcing (say a solar irradiance increase or CO2 increase) that causes a unit of warming. Let’s ask how this unit warming will be amplified by a very strong feedback, one that increases the initial warming by 50%. The added warming of 0.5 induces more feedback, by 0.5×0.5 = 0.25, and so on, the final response being 1 + 0.5 + 0.25 + 0.125 + … = 2. So this very strong feedback causes the final warming to be twice as large as it would have been without the feedback. But it is not a runaway effect. 

The strongest feedback that we observe on Earth today, from water vapor, is almost as strong as this example. Other feedbacks are occurring at the same time, some amplifying and some diminishing (negative). The net effect of all fast feedbacks can be assessed by comparing different well-characterized climate states in Earth’s history, as described in our paper,{4} treating slow changes such as ice sheet size as specified boundary conditions. It turns out that the net effect of fast feedbacks is to amplify the global temperature response by about a factor of 2-3.{b} 

Other feedbacks become important on longer time scales. As the planet becomes warmer the ice sheet area tends to decrease, exposing a darker surface that absorbs more sunlight. And as the planet warms the ocean and land release long-lived greenhouse gases, mainly CO2 and CH4 (methane). Thus Earth’s climate is dominated by amplifying feedbacks on time scales of 10-100,000 years and less. For this reason, Earth can be whipsawed between glacial and interglacial conditions by the small climate forcings caused by perturbations of Earth’s orbit.{6} 

The dominance of amplifying feedbacks and the resulting high climate sensitivity make Earth susceptible to what we can call a mini-runaway. By mini-runaway, I refer to a case with an amplifying feedback large enough that the total feedback reaches runaway (the infinite series above does not converge), but eventually that process runs out of fuel. Evidence of such behavior is provided by hyperthermal events in Earth’s history, sudden rapid warmings that occurred during periods of more gradual warming. 

The most studied hyperthermal is the PETM (Paleocene Eocene Thermal Maximum), which occurred in the middle of a 10 million year period of gradual warming. A rapid warming spike occurred in conjunction with injection of a large amount of CO2 into the climate system on a time scale of the order of a millennium. The source of the rapid CO2 increase is most commonly suggested to have been the melting of methane hydrates due to a warming ocean, with an alternative suggestion being incineration of large peat deposits, especially on Antarctica. 

Whatever the CO2 source, global temperature increased about 6°C over several millennia. The continental weathering process provided a negative feedback, as a pumped-up hydrologic cycle drew down atmospheric CO2 and deposited it as carbonate on the ocean floor. However, this feedback requires tens of thousands of years, so the rapid warming stopped only when the fuel source was depleted. 

Are hyperthermals relevant now, as a possible amplification of fossil fuel warming? Unfortunately, they may be. Burning all fossil fuels would produce such large ocean warming, which would continue to exist for centuries, that ignition of a hyperthermal amplification of global warming is a possibility. Consequences are unclear. Carbon release in prior hyperthermals occurred over a millennium or more, at a rate up to ~ 5 GtC/year. This can be compared with the present global rate of fossil fuel burning, which is ~ 9 GtC/year. 

It is instructive to consider the task of dealing with such continuing carbon release, in the event that we did set it off. Humanity could defuse a continuous release of 5 GtC/year, thus avoiding hyperthermal warming, by capturing and sequestering the carbon. The American Physical Society estimates {7} the cost of capture and sequestration as ~ $2 trillion per GtC. Given that the United States is responsible for 26% of the fossil fuel CO2 in the air today {8}, the U.S. cost share for removing 5 GtC/year would be ~$2.6 trillion each year. Technology development might be able to lower that cost, but fundamental energy constraints imply that cost reduction at most will be a factor of a few. {9} 

We had better be sure to avoid a mini-runaway. If we phase out fossil fuels rapidly and move to a clean energy future in accord with a scenario that my colleagues and I have described {8}, we could be reasonably confident of avoiding that situation. 

We know that prior interglacial periods were moderately warmer than the current (Holocene) interglacial. A fossil fuel emissions scenario similar to the one we have defined is needed for other reasons, especially for the purpose of maintaining reasonably stable shorelines, i.e., avoiding sea level rise of many meters, which would destroy thousands of coastal cities all around the world. 

In contrast, if we burn all the fossil fuels it is certain that sea level would eventually rise by tens of meters. The only argument is how soon the rise of several meters needed to destroy habitability of all coastal cities would occur. It is also possible that burning all fossil fuels would eventually set off a hyperthermal event, a mini-runaway. Is it conceivable that we could get a runaway leading all the way to the Venus Syndrome, Venus-like conditions on Earth? 

Runaway Greenhouse. Venus today has a surface pressure of about 90 bars, compared with 1 bar on Earth. The Venus atmosphere is mostly CO2. The huge atmospheric depth and CO2 amount are the reason Venus has a surface temperature of nearly 500°C.

Venus and Earth probably had similar early atmospheric compositions, but on Earth the carbon is mostly in Earth’s crust, not in the atmosphere. As long as Earth has an ocean most of the carbon will continue to be in the crust, because, although volcanoes inject crustal carbon into the atmosphere as CO2, the weathering process removes CO2 from the air and deposits it on the ocean floor as carbonates. Venus once had an ocean, but being closer to the Sun, its atmosphere became hot enough that hydrogen could escape from the upper atmosphere, as confirmed today by the extreme depletion on Venus of normal hydrogen relative to heavy hydrogen (deuterium), the lighter hydrogen being able to escape the gravitational field of Venus more readily. 

Earth can “achieve” Venus-like conditions, in the sense of ~90 bar surface pressure, only after first getting rid of its ocean via escape of hydrogen to space. This is conceivable if the atmosphere warms enough that the troposphere expands into the present stratosphere, thus eliminating the tropopause (see Fig. 7 in our paper {4} in press), causing water vapor to be transported more rapidly to the upper atmosphere, where it can be dissociated and the hydrogen can then escape to space. Thus extreme warming of the lower atmosphere with elimination of the cold-trap tropopause seems to be the essential physical process required for transition from Earth-like to Venus-like conditions. 

If Earth’s lower atmosphere did warm enough to accelerate escape of hydrogen it would still take at least hundreds of millions of years for the ocean to be lost to space. Additional time would be needed for massive amounts of CO2 to accumulate in the atmosphere from volcanoes associated with plate tectonics and convection in Earth’s mantle. So Venus-like conditions in the sense of 90 bar surface pressure and surface temperature of several hundred degrees are only plausible on billion-year time scales. 

Is it possible, with the present surface pressure of ~ 1 bar, for Earth’s surface to become so hot that that the planet is practically uninhabitable by humans? That is the situation I depicted in “Storms of My Grandchildren” {10}, which was presumed to be a consequence of burning all fossil fuels over a period of several centuries, with warming further amplified by ignition of PETM-like hyperthermal warming. Support for the possibility of large warming was provided by global climate model simulations indicating an upturn in climate sensitivity at climate forcings ~10 W/m2 (Fig. 30 in “Storms” {10}). If other forcings are unchanged, a 10 W/m2 forcing requires a CO2 increase by a factor of 4-8 times its pre-industrial amount (~280 ppm) — an increase that is possible if all extractable fossil fuels are burned {4,8}. Other complex global climate models also find an upturn in climate sensitivity or climate model “crash” when CO2 amount reaches such high levels {11}, raising the question of whether such a level of climate forcing is already trending toward a runaway greenhouse effect. 

The concept of a runaway greenhouse effect was introduced {12} by considering a highly idealized situation with specified troposphere-stratosphere atmospheric structure, a simple approximation for atmospheric radiation, and no inclusion of how clouds might change as climate changes, as is appropriate for introduction of a concept. More recent studies {13} relax some of the idealizations and are sufficient to show that Earth is not now near a runaway situation, but the idealizations are still sufficient that the studies do not provide a picture of where Earth is headed if all fossil fuels are burned. 

An alternative promising approach is to employ the fundamental equations for atmospheric structure and motions, i.e., the conservation equations for energy, momentum, mass, and water, and the ideal gas law. These equations form the core of atmospheric general circulation models and global climate models. However, today’s global models generally contain representations of so many additional physical processes that the models are difficult to use for investigations of extreme climatic situations, because invariably some approximations in the scores of equations become invalid in extreme climates. In contrast, my long-term colleague Gary Russell has developed a global model that solves the fundamental equations with the minimum additional physics needed to investigate climate sensitivity over the full range from snowball Earth to a hothouse uninhabitable planet. The additional physics includes accurate spectral dependence of solar and thermal radiation, convection, and clouds. Although the precision of the results depends on the representation of clouds, we suggest that the simple prescription employed is likely to correctly capture essence of cloud change in response to climate change. 

We use the Russell model in our paper to show that the tropopause rises in response to the global warming that occurs with larger and larger CO2 amounts (Fig. 7 in our paper {4}), and cloud cover decreases with increasing CO2. In consequence climate sensitivity initially increases as CO2 increases, consistent with the upturn of sensitivity found in more complex global climate models {11}. With the more realistic physics in the Russell model the runaway water vapor feedback that exists with idealized concepts {12} does not occur. However, the high climate sensitivity has implications for the habitability of the planet, should all fossil fuels actually be burned. Furthermore, we show that the calculated climate sensitivity is consistent with global temperature and CO2 amounts that are estimated to have existed at earlier times in Earth’s history when the planet was ice-free. 

One implication is that if we should “succeed” in digging up and burning all fossil fuels, some parts of the planet would become literally uninhabitable, with some time in the year having wet bulb temperature exceeding 35°C. At such temperatures, for reasons of physiology and physics, humans cannot survive, because even under ideal conditions of rest and ventilation, it is physically impossible for the environment to carry away the 100 W of metabolic heat that a human body generates when it is at rest {14}. Thus even a person lying quietly naked in hurricane force winds would be unable to survive. Temperatures even several degrees below this extreme limit would be sufficient to make a region practically uninhabitable for living and working. 

The picture that emerges for Earth sometime in the distant future, if we should dig up and burn every fossil fuel, is thus consistent with that depicted in “Storms” — an ice-free Antarctica and a desolate planet without human inhabitants. Although temperatures in the Himalayas may have become seductive, it is doubtful that the many would allow the wealthy few to appropriate this territory to themselves or that humans would survive with the extermination of most other species on the planet. At least one sentence in “Storms” will need to be corrected in the next edition: even with burning of all fossil fuels the tropical ocean does not “boil”. But it is not an exaggeration to suggest, based on best available scientific evidence, that burning all fossil fuels could result in the planet being not only ice-free but human-free. 

4. Summary Discussion 

The inertia of the climate system is not our friend. Because climate responds slowly, we have felt so far only about half of the effect of gases already in the air. This limited response makes it easier for people to believe that we are exaggerating the climate threat. 

Climate system inertia means that it will take several centuries for the eventual extreme global warming mentioned above to occur, if we are so foolish as to burn all of the fossil fuel resources. Unfortunately, despite the ocean’s thermal inertia, the transient climate phase this century, if we continue business-as-usual fossil fuel burning, is likely to cause an extended phase of extreme climate chaos. As ice sheets begin to shed ice more and more rapidly, our climate simulations indicate that a point will be reached when the high latitude ocean surface cools while low latitudes surfaces are warming. An increased temperature gradient, i.e., larger temperature contrast between low and high latitudes, will drive more powerful storms, as discussed in “Storms of My Grandchildren”.{10} 

The science of climate change, especially because of the unprecedented human-made climate forcing, includes many complex aspects. This complexity conspires with the nature of reporting and the scientific method itself, with its inherent emphasis of caveats and continual reassessment of conclusions, to make communications with the public difficult, even when the overall picture is reasonably clear. 

My principal objective in “retiring”, i.e., in leaving government service, is to create more time that will allow me to try to contribute more effectively to this communications effort. I also had concluded that the future of the Goddard Institute for Space Studies and its people would be better served by a younger person who could be focused on leading GISS. My own heart is turning more and more toward trying to make the science and its implications for policy clearer. 

I appreciate very much the well wishes I have received from many of you. I am not good at keeping up with e-mail correspondence, so I apologize to anyone who I may have failed to respond to. I also realize that the interview I gave regarding my retirement {3} may have left the impression that I would now be working mainly on specific actions to stem fossil fuel extraction and use. I believe all the individual actions occurring at many places are very important and the sum of them may help turn the tide to clean energies. But I must keep up with and contribute to climate science or I cannot be effective, so I hope to be doing more science rather than less — and science requires more than 40 hours a week — so it is not practical for me to respond to all the requests that I am receiving. I also want to support two or three people working with me, so I need to spend time in fund raising – and I am finding that it is not easy to get foundation support. I hope that papers and testimony that I provide for cases of Our Children’s Trust, or cases regarding coal exports, tar sands and other unconventional fossil fuels, can find wider use with little modification. I will continue to support the growing 350.org movement. I support CitizensClimateLobby.org especially, because of their focus on fee-and-dividend, which I believe is the sine qua non for phase out of fossil fuels. I hope you noticed the op-ed supporting fee-and-dividend in the Wall Street Journal by George Shultz and Gary Becker {15}, who point out that fee-and-dividend plus removal of energy subsidies would provide a level playing field and be good for the economy and jobs. There is also a Democratic (Boxer/Sanders) bill in Congress, but as usual they cannot keep their hands off our wallets, proposing to take 40% of the money to make government bigger, including congressional specification of how 15% of the money is to be spent. Washington seems likely to remain dysfunctional on climate policy, so when we get a bit closer to 2016 I will argue why I think we need a third party. In the meantime we must try to do what we can with what we have. Somebody with access to the President should wake him up to the implications of going down the unconventional fossil fuels route (I have tried, but failed to get access). He will have a heck of a lousy legacy if he takes the big step down that road with the Keystone pipeline. This is an area where he could reach across the aisle, suggesting that he is open to the idea of a revenue neutral carbon fee, which would save much more carbon than the Keystone pipeline would carry, but he would have to give up the Democratic penchant for telling us how to spend our money. 

Finally, I recognize that in this Summary Discussion I failed to answer the question “How can we pass from “jumping the gun” to unavoidable deleterious consequences without passing through demands for common sense policy actions?” Delving into that matter requires getting into how our government functions and fails to function. That is a big subject and, as you can see, I am running out of steam for this present communication.

Climate Change Could Turn Earth into Venus: Stephen Hawking. Telesur. Jan. 11, 2018.

the British physicist warns Earth could soon become as hot as Venus if action to halt climate change is not taken immediately. 

Hawking says Venus was once an Earth-like planet with surface water, mild temperatures and an appropriate atmosphere. According to NASA, Venus was an inhabitable planet for a period of about two billion years as recently as four billion years ago. 

Now temperatures on Venus reach 250°C with powerful 300mph winds. Hawking says a greenhouse effect burned the planet's oceans and lands, and that something similar could happen right here on Earth if climate change continues unabated. 

"Next time you meet a climate-change denier, tell them to take a trip to Venus; I will pay the fare," says the physicist

land area needed to sequester CO2 by planting trees. Jason Box. Nov. 16, 2015.

Question: What fraction of Earth’s land area would be needed to sequester the 50 ppm CO2 surplus we currently have in our atmosphere, 50 ppm above the upper safe limit of 350 ppm?

It’s not a fraction, per se. No. Seven times Earth’s land area would need to be in cultivation. I earlier had a more optimistic value based on 30 tons per hectare, half the Earth’s land area would need to be in cultivation. Yet, unfortunately, the associated crops are not suited for long term sequestration.

ps. The calculations are on one of the 9 benefits of the massive scale tree planting I believe we need to increase climate stability and peace globally:

1. carbon sequestration
2. humidification of ground and air
3. wildlife habitat restoration
4. food production
5. human habitat creation
6. employment in forestry and related industry
7. sustainable timber production
8. sustainable economic development modeling
9. hope

Scientist Quotes #1

"Climate change is coming at us faster, with larger impacts and bigger risks, than even most climate scientists expected as recently as a few years ago. The stated goal of the UNFCCC – avoiding dangerous anthropogenic interference in the climate – is in fact unattainable, because today we are already experiencing dangerous anthropogenic interference. The real question now is whether we can still avoid catastrophic anthro-pogenic interference in climate. There is no guarantee that catastrophe can be avoided even we start taking serious evasive action immediately; But it’s increasingly clear that the current level of anthropogenic interference is dangerous: Significant impacts in terms of floods, droughts, wildfires, species, melting ice already evident at ~0.8°C above pre-industrial Tavg. Current GHG concentrations commit us to 0.6°C more."

John Holdren, Director, Woods Hole Research Centre, leading climate scientist, Nov 3, 2006.

"If there's no action before 2012, that's too late. What we do in the next two to three years will determine our future. This is the defining moment."
Rajendra Pachauri, Chair of the UN Intergovernmental Panel on Climate Change, Nov 17, 2007.

Global climate change and other ongoing persistent global environmental problems "threaten humanity's very survival.... The need couldn't be more urgent ... to act now to safeguard our own survival and that of future generations."
UNEP GEO-4, 2007

"We have reached a point of planetary emergency,'' he said. "There are tipping points in the climate system, which we are very close to, and if we pass them, the dynamics of the system take over and carry you to very large changes which are out of your control."

James Hansen, Jun 24, 2008.

"The potential for runaway greenhouse warming is real and has never been more clear."
UNEP Year Book, 2009

"For humanity it's a matter of life or death," he said. "We will not make all human beings extinct, as a few people with the right sort of resources may put themselves in the right parts of the world and survive. But I think it's extremely unlikely that we wouldn't have mass death at 4C. If you have got a population of nine billion by 2050 and you hit 4C, 5C or 6C, you might have half a billion people surviving".

Kevin Anderson, Deputy Director of the Tyndall Centre for Climate Change Research and joint chair in Energy and Climate Change at the School of Mechanical, Aerospace and Civil Engineering at the University of Manchester and School of Environmental Sciences at the University of East Anglia. Nov 29, 2009.

in response to the question “what has to be done?” stated: 

“extremely rapid reduction in emissions … I would say, 80 percent within the next ten years or so … people like me have been looking at the evidence about this on a day to day basis and we have been doing it for years, and to look in to the abyss at this length is a daunting task.”

Andrew Glikson, paleoclimate scientist, Australia National University, July 2009.

“My view is that the climate has already crossed at least one tipping point, about 1975-1976, and is now at a runaway state, implying that only emergency measures have a chance of making a difference…”  

Andrew Glikson, 2010

"analysis suggests that despite high-level statements to the contrary, there is now little to no chance of maintaining the global mean surface temperature at or below 2°C. Moreover, the impacts associated with 2°C have been revised upwards, sufficiently so that 2°C now more appropriately represents the threshold between 'dangerous' and 'extremely dangerous' climate change."

Kevin Anderson and Alice Bows, Nov 29, 2010.

"Humans have already set in motion 69 feet of sea level rise."

Jason Box, professor in glaciology at the Geological Survey of Denmark and Greenland, Jan 31, 2013.

"It is the summer sea ice loss passing point of no return, leading to unstoppable catastrophic Arctic Methane feedbacks sooner or later ... puts us in a planetary emergency today."
John Nissen. Arctic Methane Emergency Group. Dec 4, 2014.

"If even a small fraction of Arctic sea floor carbon is released to the atmosphere, we're f'd."
Jason Box. Jul 7, 2015.

"We are in a kind of climate emergency now... It is becoming more and more urgent. Time has almost run out to get emissions down. That’s the real emergency."

Prof Stefan Rahmstorf, Potsdam Institute for Climate Impact Research. Mar 14, 2016.

Feature Reference Articles #1

Excerpts from feature reference articles

The awful truth about climate change no one wants to admit. David Roberts, vox. May 15, 2015.

"A 4°C warmer world can, and must be, avoided," said the World Bank president. 

But that's where we're headed. It will take enormous effort just to avoid that fate. Holding temperature down under 2°C — the widely agreed upon target — would require an utterly unprecedented level of global mobilization and coordination, sustained over decades. There's no sign of that happening, or reason to think it's plausible anytime soon. And so, awful shit it is....

Climate scientists, Geden says, feel pressure to provide the good news. They're worried that if they don't, if they come off as "alarmist" or hectoring, they will simply be ignored, boxed out of the debate. And so they construct models showing that it is possible to hit the 2°C target. The message is always, "We're running out of time; we've only got five or 10 years to turn things around, but we can do it if we put our minds to it." That was the message in 1990, in 2000, in 2010. How can we still have five or 10 years left? The answer, Geden says, is that scientists are baking increasingly unrealistic assumptions into their models.

 

Limiting Global Warming to 2 Degrees Celsius Won’t Save Us. Kate Dooley and Peter Christoff, New Republic. May 27, 2015.

Can we limit warming to 1.5 degrees Celsius? 

The 2 degrees Celsius warming limit or “guardrail” has long been controversial. It was rejected by many developing countries at Copenhagen and over two thirds of Parties to the Convention call for a 1.5 degrees Celsius limit. So is this ambitious temperature limit still within reach? 

The carbon budget approach—adopted by the IPCC in its latest report—defines the amounts of cumulative CO2 emissions which will drive warming to a given global temperature limit. The most stringent IPCC scenario gives a remaining (from 2011) carbon budget of 1,000 billion tonnes of CO2, for a “likely” chance of keeping global temperature within 2 degrees Celsius.

Yet whether a lower temperature limit is still within reach, and the pathway to get there, is debated. The more ambitious mitigation scenarios reported by the IPCC are characterized by overshooting the budget and then removing greenhouse gases from the atmosphere. This usually means relying on bioenergy plus carbon capture and storage (burning biomass for energy, removing the CO2, and then storing it underground) to remove carbon from the atmosphere—which comes with its own risks.

1.5 degrees Celsius pathways which do not rely on negative emissions depend on a much lower remaining budget. Even a 50 percent chance of keeping below 1.5 degrees Celsius requires immediate and radical emission reductions. This would mean unprecedented annual rates of decline which are not in line with current levels of energy consumption or ideas of economic growth...

The UNFCC expert group recognized that limiting global warming to below even 2 degrees Celsius necessitates a radical transition, not merely a fine-tuning of current trends, yet such radical emissions reduction pathways are so far excluded from IPCC assessment, leaving policy makers with little evidence on the impacts and feasibility of lower targets.

Where to from here?

The group concluded that the world is not on track to achieve the long-term global goal of 2 degrees Celsius, noting that the longer we wait to bend the curve of global greenhouse gas emissions, the steeper we will have to bend it down later.

Two degrees: The world set a simple goal for climate change. We're likely to miss it. Brad Plumer, vox. Apr. 22, 2014.

It was the early 1990s. Climate scientists had long known that humans were warming up the planet. But politicians were only beginning to appreciate that it would take a staggering coordinated effort to get nations to burn fewer fossil fuels and avoid sharp temperature increases in the decades ahead. 

Those policymakers needed a common goal — a way to say, Here’s how bad things will get and This is what we need to do to stop it. But that posed a dilemma. No one could agree on how much global warming was actually unacceptable. How high did the seas need to rise before we had a serious problem? How much heat was too much? 

Around this time, an advisory council of scientists in Germany proposed an alluringly simple way to think about climate change. Look, they reasoned, human civilization hasn’t been around all that long. And for the last 12,000 years, Earth’s climate has fluctuated within a narrow band. So, to be on the safe side, we should prevent global average temperatures from rising more than 2° Celsius (or 3.6° Fahrenheit) above what they were just before the dawn of industrialization. 

Critics grumbled that the 2°C limit seemed arbitrary or overly simplistic. But scientists were soon compiling evidence that the risks of global warming became fairly daunting somewhere above the 2°C threshold: rapid sea-level rise, the risk of crop failure, the collapse of coral reefs. And policymakers loved the idea of a simple, easily digestible target. So it stuck. 

By 2009, nearly every government in the world had endorsed the 2°C limit — global warming beyond that level was widely considered "dangerous." And so, every year, the world’s leaders meet at UN climate conferences to discuss policies and emissions cuts that they hope will keep us below 2°C. Climate experts churn out endless papers on how we can adapt to 2°C of warming or less. 

Two decades later, there’s just one huge problem with this picture. The idea that the world can stay below 2°C looks increasingly delusional.

John H. Richardson: When the End of Human Civilization is Your Day Job. Esquire. July 7, 2015.

Among many climate scientists, gloom has set in. Things are worse than we think, but they can’t really talk about it.

Jason Box: "If even a small fraction of Arctic sea floor carbon is released to the atmosphere, we're f'd."

Now, with one word, Box had ventured into two particularly dangerous areas. First, the dirty secret of climate science and government climate policies is that they're all based on probabilities, which means that the effects of standard CO2 targets like an 80 percent reduction by 2050 are based on the middle of the probability curve. Box had ventured to the darker possibilities on the curve's tail, where few scientists and zero politicians are willing to go.

As a recent study from the University of Bristol documented, climate scientists have been so distracted and intimidated by the relentless campaign against them that they tend to avoid any statements that might get them labeled "alarmists," retreating into a world of charts and data.

"I think most scientists must be burying overt recognition of the awful truths of climate change in a protective layer of denial (not the same kind of denial coming from conservatives, of course). I'm still amazed how few climatologists have taken an advocacy message to the streets, demonstrating for some policy action." 

...a study by the U. S. Navy says that the Arctic could lose its summer sea ice by next year, eighty-four years ahead of the models

And yet, despite some encouraging developments in renewable energy and some breakthroughs in international leadership, carbon emissions continue to rise at a steady rate, and for their pains the scientists themselves—the cruelest blow of all—have been the targets of an unrelenting and well-organized attack that includes death threats, summonses from a hostile Congress, attempts to get them fired, legal harassment, and intrusive discovery demands so severe they had to start their own legal-defense fund, all amplified by a relentless propaganda campaign nakedly financed by the fossil-fuel companies. Shortly before a pivotal climate summit in Copenhagen in 2009, thousands of their e-mail streams were hacked in a sophisticated espionage operation that has never been solved

Michael E. Mann: How Close Are We to ‘Dangerous’ Planetary Warming?. Huffington Post. Dec. 23, 2015.

It has been widely reported that 2015 will be the first year where temperatures climbed to 1C above the pre-industrial. That might make it seem like we’ve got quite a ways to go until we breach the 2C limit. But the claim is wrong. We exceeded 1C warming more than a decade ago. The problem is that here, and elsewhere, an inappropriate baseline has been invoked for defining the “pre-industrial.” The warming was measured relative to the average over the latter half of the 19th century (1850-1900). In other words, the base year implicitly used to define “pre-industrial” conditions is 1875, the mid-point of that interval. Yet the industrial revolution and the rise in atmospheric CO2 concentrations associated with it, began more than a century earlier

The IPCC graphic suggests that keeping net CO2 emissions below 3 trillion tons — and thereby stabilizing maximum CO2 concentrations below 450 ppm — would likely keep warming below the “dangerous” 2C limit. Unfortunately, that conclusion is overly optimistic because, once again, it relies on the use of an artificially warm, too-recent baseline for defining the pre-industrial period roughly 0.3C greenhouse warming had already taken place by 1900, and roughly 0.2C warming by 1870

When we take this factor into account (orange dotted curve), the warming for 450 ppm stabilization is now is seen to approach 2.5C, well about the “dangerous” limit. Indeed, CO2 concentrations now have to be kept below 405 ppm (where we’ll be in under three years at current rates of emissions) to avoid 2C warming (blue dotted curve). 

So evidently, we don’t have 1/3 of our total carbon budget left to expend, as implied by the IPCC analysis. We’ve already expended the vast majority of the budget for remaining under 2C. And what about 1.5C stabilization? We’re already overdrawn. 

The more we delay rapid reductions in fossil fuel burning, the more we will need to offset additional carbon emissions by sequestration of atmospheric carbon, either through massive reforestation projects, or ‘geoengineering’ technology such as “direct air capture,” which involves literally sucking the CO2 back out of the atmosphere

Michael E. Mann. Earth Will Cross the Climate Danger Threshold by 2036. Scientific American. April 1, 2014.

The rate of global temperature rise may have hit a plateau, but a climate crisis still looms in the near future.

If the world continues to burn fossil fuels at the current rate, global warming will rise to two degrees Celsius by 2036, crossing a threshold that will harm human civilization. To avoid the threshold, nations will have to keep carbon dioxide levels below 405 parts per million. 

In its September 2013 report, the IPCC extended the stick back in time, concluding that the recent warming was likely unprecedented for at least 1,400 years. 

Although the earth has experienced exceptional warming over the past century, to estimate how much more will occur we need to know how temperature will respond to the ongoing human-caused rise in atmospheric greenhouse gases, primarily carbon dioxide. Scientists call this responsiveness “equilibrium climate sensitivity” (ECS). ECS is a common measure of the heating effect of greenhouse gases. It represents the warming at the earth's surface that is expected after the concentration of CO2 in the atmosphere doubles and the climate subsequently stabilizes (reaches equilibrium). 

The preindustrial level of CO2 was about 280 parts per million (ppm), so double is roughly 560 ppm. Scientists expect this doubling to occur later this century if nations continue to burn fossil fuels as they do now—the “business as usual” scenario—instead of curtailing fossil-fuel use. The more sensitive the atmosphere is to a rise in CO2, the higher the ECS, and the faster the temperature will rise. ECS is shorthand for the amount of warming expected, given a particular fossil-fuel emissions scenario. 

It is difficult to determine an exact value of ECS because warming is affected by feedback mechanisms, including clouds, ice and other factors. Different modeling groups come to different conclusions on what the precise effects of these feedbacks may be. Clouds could be the most significant. They can have both a cooling effect, by blocking out incoming sunlight, and a warming effect, by absorbing some of the heat energy that the earth sends out toward space. Which of these effects dominates depends on the type, distribution and altitude of the clouds—difficult for climate models to predict. Other feedback factors relate to how much water vapor there will be in a warmer atmosphere and how fast sea ice and continental ice sheets will melt. 

Because the nature of these feedback factors is uncertain, the IPCC provides a range for ECS, rather than a single number 

An ECS of three degrees C means that if we are to limit global warming to below two degrees C forever, we need to keep CO2concentrations far below twice preindustrial levels, closer to 450 ppm. Ironically, if the world burns significantly less coal, that would lessen CO2emissions but also reduce aerosols in the atmosphere that block the sun (such as sulfate particulates), so we would have to limit CO2 to below roughly 405 ppm. 

The conclusion that limiting CO2 below 450 ppm will prevent warming beyond two degrees C is based on a conservative definition of climate sensitivity that considers only the so-called fast feedbacks in the climate system, such as changes in clouds, water vapor and melting sea ice. Some climate scientists, including James E. Hansen, former head of the NASA Goddard Institute for Space Studies, say we must also consider slower feedbacks such as changes in the continental ice sheets. When these are taken into account, Hansen and others maintain, we need to get back down to the lower level of CO2 that existed during the mid-20th century—about 350 ppm.

Michael E. Mann is Distinguished Professor of Meteorology at Pennsylvania State University and contributed to the International Panel on Climate Change work that received the 2007 Nobel Peace Prize. He has written the book The Hockey Stick and the Climate Wars: Dispatches from the Front Lines, as well as Dire Predictions: Understanding Global Warming.

related research:
Defining Dangerous Anthropogenic Interference. Michael E. Mann in Proceedings of the National Academy of Sciences USA, Vol. 106, No. 11, pages 4065–4066; March 17, 2009.

Separating Forced from Chaotic Climate Variability over the Past Millennium. Andrew P. Schurer et al. in Journal of Climate, Vol. 26, No. 18, pages 6954–6973; September 2013.


John Carey. Is Global Warming Happening Faster Than Expected? Scientific American. November 1, 2012.

Loss of ice, melting of permafrost and other climate effects are occurring at an alarming pace.

Keeping planetary warming below two degrees Celsius (3.6 degrees Fahrenheit) would, it was thought, avoid such perils as catastrophic sea-level rise and searing droughts. Staying below two degrees C would require limiting the level of heat-trapping carbon dioxide in the atmosphere to 450 parts per million (ppm), up from today's 395 ppm and the preindustrial era's 280 ppm.

an example of how alarm bells were being rung over 5 years ago:
The brutal logic of climate change. David Roberts, Grist. Dec 6, 2011.

As you can see, the 2 degrees C “guardrail” that separated acceptable from dangerous in 2001 is, in 2009, squarely inside several red zones. Today, the exact same social and political considerations that settled on 2 degrees C as the threshold of safety by all rights ought to settle on 1 degree C [1.8 degrees F]. After all, we now know 2 degrees C is extremely dangerous. 

At this point, however, stopping at 1 degree C is physically impossible (we can thank our past inaction for that). Indeed, as we’ll see, stopping at 2 degrees C is getting close to impossible as well. There is no longer any reasonable chance of avoiding “dangerous” climate change, so 1 degree C vs. 2 degrees C is a somewhat academic debate. At this point we’re just shooting to avoid super-duper-dangerous. ...

The thing is, if 2 degrees C is extremely dangerous, 4 degrees C is absolutely catastrophic. In fact, according to the latest science, says Anderson, “a 4 degrees C future is incompatible with an organized global community, is likely to be beyond ‘adaptation’, is devastating to the majority of ecosystems, and has a high probability of not being stable.”...

Oh, and by the way: According to the International Energy Agency, we’re currently on course for 6 degrees C [10.8 degrees F]. That is, beyond any reasonable doubt, game over.

Oliver Geden: Climate advisers must maintain integrity. Nature. May 6, 2015.

The negotiations' goal has become what is politically possible, not what is environmentally desirable. Gone is a focus on establishing a global, 'top down' target for stabilizing emissions or a carbon budget that is legally binding. The Paris meeting will focus on voluntary, 'bottom up' commitments by individual states to reduce emissions. 

There is another casualty: scientific advice. Climate scientists and economists who counsel policy-makers are being pressured to extend their models and options for delivering mitigation later. This has introduced dubious concepts, such as repaying 'carbon debt' through 'negative emissions' to offset delayed mitigation — in theory.
Scientific advisers must resist pressures that undermine the integrity of climate science. Instead of spreading false optimism, they must stand firm and defend their intellectual independence, findings and recommendations — no matter how politically unpalatable 

Climate researchers who advise policy-makers feel that they have two options: be pragmatic or be ignored. They either distance themselves from the policy process by declaring that it is no longer possible to stay within a 2 °C-compatible carbon budget, or they suggest practical ways to dodge carbon-budget constraints3. 

Many advisers are choosing pragmatism. This can lead to paradoxical positions, as exemplified by shifting assumptions in climate economics over the past few years. 

Each year, mitigation scenarios that explore policy options for transforming the global economy are more optimistic4 — and less plausible. Advisers once assumed that the global emissions peak would have to be reached before 2020 and that annual emissions-reduction rates of more than 3% were not feasible. Those assumptions keep changing. 

For example, the fourth assessment of the Intergovernmental Panel on Climate Change (IPCC), published in 2007, stated that emissions must peak by 2015 to stay within 2 °C of warming; yet the fifth IPCC report, released last year, refers to 2030 emissions levels higher than today's that are still compatible with this limit, albeit with annual emissions-reduction rates of 6%

climate economists got around past 'make-or-break' points for the 2 °C target by adding 'negative emissions' — the removal of greenhouse gases from the atmosphere during the second half of this century. Most models assume that this can be achieved using a combination of approaches known as BECCS: bioenergy (which would require 500 million hectares of land — 1.5 times the size of India)4 and carbon capture and storage, an unproven technology.

The climate policy mantra — that time is running out for 2 °C but we can still make it if we act now — is a scientific nonsense. Advisers who shy away from saying so squander their scientific reputations and public trust in climate research 

Everyday politics is therefore dominated not by evidence-based policy-making but by attempts at 'policy-based evidence-making'.  

Jonathan Chait: Climate Change and Conservative Brain Death. New York Magazine. March 14, 2016.

asked about climate change, and Marco Rubio supplied an answer that, while banal and dogmatic, was fascinating in its own way… Rubio repeated his formulaic and un-categorical opposition to any policy to limit the greenhouse-gas emissions that are in the process of sinking his home city. Rubio’s reply was not just the last gasp of a dying campaign, but a state-of-the-art expression of party doctrine. Trump is what the regular Republicans are trying to stave off; Rubio represents what they are fighting to preserve: a delusional anti-government ideology unable to process or cope with real-world conditions. 

The green-energy revolution is really two revolutions acting in tandem: an increase in political willpower, and the rise of new technologies to reduce carbon usage. The two forces interact with each other in powerful ways. As elected officials commit to emissions reductions, the market invests in clean energy technologies, bringing down their price; and as transitioning to lower emissions gets cheaper and more convenient, elected officials can promise deeper reductions still. Rubio revealed the mind-set of a party that remains fully in denial of all this — not just the science but the diplomatic and technological transformation now well under way. The horror of the populist insurgency besieging the GOP from its perimeter has diverted attention from the deep intellectual rot at its core 

Dr. Gideon Polya: G7 Pledge of Zero Emissions by 2100 Masks Worsening Climate Emergency and Need for Urgent Action. June 10, 2015.

The June 2015 G7 pledges of  (a) zero emissions by 2100 and (b) avoidance of a plus 2 degrees C  temperature rise were greeted as “the end of fossil fuels”. Unfortunately (a) the World will exceed its Terminal Carbon Budget for a 75% probability of avoiding plus 2 degrees C in about 3 years, and (b) a plus 2 degrees C temperature  rise is disastrous for Humanity and the Biosphere, yielding at equilibrium  sea levels “at least  6 to 8 metres higher” according to Dr James Hansen of NASA 

Dr Andrew Glikson (a paleoclimate scientist and earth scientist, ANU, Canberra, Australia) (2008),  “For some time now, climate scientists warned that melting of subpolar permafrost and warming of the Arctic Sea (up to 4 degrees C during 2005–2008 relative to the 1951–1980) are likely to result in the dissociation of methane hydrates and the release of this powerful greenhouse gas into the atmosphere 

Dr. T. Goreau (President of the Global Coral Reef Alliance, an international NGO for restoration of coral reefs, and a member of the Jamaican delegation to UNCCC;  previously Senior Scientific Affairs Officer at the United Nations Centre for Science and Technology for Development, in charge of Global Climate Change and Biodiversity issues, where he contributed to the original draft of the UN Framework Convention on Climate Change) (2009):  “The long-term sea level that corresponds to current CO2 concentration is about 23 meters above today's levels, and the temperatures will be 6 degrees C or more higher. These estimates are based on real long term climate records, not models" 

Dr James Hansen (a leading US climate scientist, former  head of the NASA Goddard Institute for Space Studies in New York City, a part of the Goddard Space Flight Center in Greenbelt, Maryland, an adjunct professor in the Department of Earth and Environmental Sciences at Columbia University, first warned the US Congress about the danger from man-made climate change over 20 years ago, and  published “Storms of My Grandchildren” in 2009) (2015):  “2 degrees is actually a prescription for disaster. That's actually well understood by the scientific community. We know that the prior interglacial period about 120,000 years ago – its called the Eemian in Europe – was less than 2C warmer than pre-industrial conditions and sea level was a least 6 to 8 metres higher, so it's crazy to think that 2 degrees Celsius is a safe limit… make the  price of fossil fuels honest”

Renewable Energy After COP21: Nine issues for climate leaders to think about on the journey home.
Richard Heinberg, Post Carbon Institute, Dec 14, 2015.


UN Predicts Disaster if Global Warming Not Checked. Peter James Spielmann, AP News Archive. Jun 29, 1989.

Noel Brown, director of the New York office of the U.N. Environment Program, or UNEP, said governments have a 10-year window of opportunity to solve the greenhouse effect before it goes beyond human control.... He said even the most conservative scientists ''already tell us there's nothing we can do now to stop a ... change'' of about 3 degrees.