This chart shows temp
relative to the 1961-1990 average
So, as you can see, the
period from 1850-1900 was well below 1961-90, while 1990-2018 are well above
On net, we are very
much well in excess of pre-industrial temperature norms (which is important
because the global goals is to keep the planet from being destabilized by keeping
temp increase contained to no more than 2C above pre-industrial, and
preferrably 1.5C)
Those temp changes are
manifesting themselves in other ways
And these other
impacts will themselves in turn have a feedback effect on temperatures,
creating a vicious circle
So far, that just
covers what has happened so far… here’s what we’re looking at for the future
This shows just two
possible scenarios, business as usual, what IPCC calls RCP8.5, and something
that many would consider a best case, RCP2.6
Note how on the path
we are on, which means continued economic growth, which means more consumption
of everything, and more use of energy, which so far is predominantly
fossil-fuels, CO2 concentrations in the atmosphere will rise not just linearly
but exponentially; on the other hand, in order for us to achieve that best-case
2.6 scenario we just mentioned, you can see that rather than having emissions
keep growing, we need to have them quickly plateau and head to zero, and, in
fact, below zero (meaning we utilize new technologies to extract more carbon
from the atmosphere than we put in)
Some people think,
hey, we live in Canada, its cold, no big deal if it gets warmer
Except, for one thing,
temperatures are rising further and faster here in Canada than globally, and
especially up north in the Arctic
Canada is warming at
twice the global rate, and the Arctic at thrice the global rate.. that is
hugely destabilizing
So while it might seem
okay in southern Ontario, we need to worry about those feedback effects we
mentioned earlier… as the Arctic warms, not only are polar bears and other
wildlife at risk, but less snow and ice means less albedo effect, and warming
tundra means melting permafrost, which releases methane, a very potent GhG into
the atmosphere, both from land and from the seabeds, which will cause a huge
feedback effect, and greatly accentuate warming, to the extent that it can
spiral out of control (Hothouse Earth scenario)
Here’s what climate
models, as of the 2013 IPCC report, say will happen to global temperatures as
we continue to emit emissions
2 things to note about
that:
- these are the projected global avg changes, and, as we just saw, Canada will warm twice as much and the Arctic thrice as much
- global climate change models have improved in the last 6 years, and the latest estimates suggest the climate is even more sensitive than we previously thought, so temperatures will rise even further and faster than is shown here
Note that the majority
of climate scientists consider it unlikely that we will fall below the low
ranges of the above estimates, but remain concerned that we could exceed the
high ranges (which already allow for 25% chance of being exceeded).. but could
be worse due to feedback effects, tipping points and irreversibilities in the
climate system
If we see these types
of temperature changes in the 8.5 scenario, imagine the impacts related to:
·
hot and
cold extremes
o
i.e.
greater weather variability than we’ve experienced this year
·
extreme
weather events,
o
causing flooding
on the one hand, and
o
droughts
on the other
·
and
related knock-on effects on
o
groundwater
and freshwater availability
o
our
agricultural sector, our growing season, etc.
·
wildfires
·
ocean
temperature and ocean acidification
o
and
impacts on fisheries
·
sea level
rise
o
storm
surges for our coastal infrastructure / cities
Uncertainties prevail!
Keep in mind that most estimates we see from models are based on chances /
estimates
There are still
significant risks of things being worse than we currently judge (and over the
last 30 years, that has typically been the case, that outcomes have been
generally worse than earlier anticipated)
Which raises the
question of whether we want to accept a 50% or 25% or even 10% chance of
temperatures getting even higher
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