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Until recently, climate scientists didn't spend much time on using their climate change models to make projections of the worst case scenarios that we would face if we continued "Business as Usual" -- if we didn't make the changes needed to avoid catastrophic global warming.
Scientists didn't think that mankind could be that stupid.
But alas, Republicans and modern day Conservatives (who are any thing but "conservative") rose to the challenge and have proven that mankind can indeed be that stupid. Furthermore, they have effectively prevented any political action that would change our "Business as Usual" way of doing things.
So scientists finally have gotten the message and some of them has started to do serious work to predict what will happen by 2050, 2100 and beyond if we do indeed continue BAU.
Under BAU, we are easily facing the prospect of climate change as great as the difference between the last glacial period and our current interglacial period -- the by end of this century.
Now that is a very significant change. Much of Minnesota was under ice sheets about a mile or so thick during the last glacial period.
Here below is a review of what some of the predictions are. Keep in mind that scientists are by nature conservative (unlike Conservatives) and their model predictions are usually on the conservative side. So, if we continue BAU, things will probably be worse that the predictions presented below.
The projections below are only based on C02 levels -- just about 400ppm at present. When you add in the other greenhouse gases we have added to the atmosphere, we are already at 480ppm C02 equivalence.
Roy Hagen in Nairobi
By Joe Romm on
October 14, 2012 at 12:30 pm
"An Illustrated Guide to the Science of Global Warming Impacts: How We Know Inaction Is the Gravest Threat Humanity Faces"
Humanity’s Choice (via M.I.T.):
Inaction (“No Policy”) eliminates most of the uncertainty about
whether future warming will be catastrophic. Aggressive emissions
reductions greatly improves humanity’s chances.
In this post, I will summarize what the recent scientific literature
says are the key impacts we face in the coming decades if we stay
anywhere near our current emissions path. These include:
- Staggeringly high temperature rise, especially over land — some 10°F over much of the United States
- Permanent Dust Bowl conditions over the U.S. Southwest and many
other regions around the globe that are heavily populated and/or heavily
farmed.
- Sea level rise of some 1 foot by 2050, then 4 to 6 feet (or more) by
2100, rising some 6 to 12 inches (or more) each decade thereafter
- Massive species loss on land and sea — perhaps 50% or more of all biodiversity.
- Unexpected impacts — the fearsome “unknown unknowns”
- Much more extreme weather
- Food insecurity — the increasing difficulty of feeding 7 billion,
then 8 billion, and then 9 billion people in a world with an
ever-worsening climate.
- Myriad direct health impacts
Remember,
these will all be happening simultaneously and getting worse decade after decade. Equally tragic, a 2009 NOAA-led study found the worst impacts would be
“largely irreversible for 1000 years.”
The single biggest failure of messaging by climate scientists (until
very recently) has been the failure to explain to the public, opinion
makers, and the media that business-as-usual warming results in
simultaneous, ever-worsening impacts that, individually, are each
beyond catastrophic, but combined are unimaginablly horrific. For
these impacts, terms like “global warming” and “climate change” are
essentially euphemisms. That is why I have preferred the term “Hell and
High Water.”
By virtue of their success in promoting doubt and inaction, the
climate science deniers and disinformers have, tragically and
ironically, turned the worst-case scenario into business as usual.
Business as usual typically means continuing at recent growth rates
of carbon dioxide emissions, which we now know would likely take us to
atmospheric concentrations of CO2 greater than 850 ppm if not above 1000
ppm (see
U.S. media largely ignores latest warning from climate scientists:
“Recent observations confirm … the worst-case IPCC scenario
trajectories are being realised”). Annual emissions now exceed 10
billion metric tons of carbon (~37 billions metric tons of CO2).
Emissions have been rising about 3% per year for the past decade.
What is less well understood is that even a very strong mitigation
effort that kept carbon emissions this century to 11 billion tons a year
on average would still probably take us to 1000 ppm (A1FI scenario) — a
little noted conclusion of the 2007 Intergovernmental Panel on Climate
Change (IPCC) report (see “
Nature publishes my climate analysis and solution“).
Until recently, the scientific community has spent little time
modeling the impacts of a tripling (~830 ppm) or quadrupling (~1100 ppm)
carbon dioxide concentrations from preindustrial levels. In part, I
think, that’s because they never believed humanity would be so
self-destructive as to ignore their science-based warnings and simply
continue on its unsustainable path. In part, they lowballed the
difficult-to-model amplifying feedbacks in the carbon cycle.
In a 2010 AAAS presentation, the late William R. Freudenburg of UC Santa Barbara discussed his research on “
the Asymmetry of Scientific Challenge“:
New
scientific findings since the 2007 IPCC report are found to be more
than twenty times as likely to indicate that global climate
disruption is “worse than previously expected,” rather than “not
as bad as previously expected.”
This post will review the latest findings. It will serve as a
foundation for a multi-part series that attempts to clear up some of the
confusion over the supposed high degree of “uncertainty” surrounding
climate impacts. That series will make clear that we have an unusually high degree of certainty around future climate impacts if we stay anywhere near our current emissions path.
This post —
an update
— covers more than 60 recent scientific studies along with numerous
review pieces that themselves each cover a large segment of the recent
literature. Please add links to more studies in the comments.
We will see why
inaction on climate change is “incompatible
with organized global community, is likely to be beyond ‘adaptation’,
is devastating to the majority of ecosystems & has a high
probability of not being stable (i.e. 4°C [7F] would be an interim
temperature on the way to a much higher equilibrium level),” according to Professor Kevin Anderson, director of the Tyndall Centre for Climate Change in Britain (see
here).
TEMPERATURE
Three of the best recent analyses of what we are headed towards can be found here:
As Dr. Vicky Pope, Head of Climate Change Advice for the Met Office’s Hadley Centre has explained:
… where no action is taken to check the rise in
Greenhouse gas emissions, temperatures would most likely rise by more
than 5°C by the end of the century. This would lead to significant risks of severe and irreversible impacts.
That likely rise corresponds to roughly 9°F globally and typically
40% higher than that over inland mid-latitudes (i.e. much of this
country) — or well over 10°F.
[
Note: The MIT rise is compared to 1980-1999 levels -- see study here). So you can add at least 0.5 C and 1.0°F for comparison with pre-industrial temperatures.]
By century’s end, extreme temperatures of up to 122°F would
threaten most of the central, southern, and western U.S. Even worse,
Houston and Washington, DC could experience temperatures exceeding 98°F
for some 60 days a year. Much of Arizona would be subjected to temperatures of 105°F or more for 98 days out of the year–14 full weeks.
Yet that conclusion is based on studies of only 700 ppm and 850 ppm, so it could get much hotter than that.
And the Hadley Center adds, “By the 2090s close to one-fifth of the
world’s population will be exposed to ozone levels well above the World
Health Organization recommended safe-health level.”
The MIT press
release
called for “rapid and massive” action to avoid this. Study co-author
Ronald Prinn, the co-director of the Joint Program and director of MIT’s
Center for Global Change Science, said, it is important “to base our
opinions and policies on the peer-reviewed science….
There’s no way the world can or should take these risks.” Duh!
MIT put together a good figure that compares the temperatures we risk
on our current do-nothing path with those we might expect if we took
serious action [see top figure above]. Note that in the “no policy
case” there is an extremely high probability of more than 4°C (7°F)
global warming, and about a 25% chance of more than 6°C (11°F) global
warming.
In a 2010 presentation, Climate scientist Katherine Hayhoe has a
figure of what 1000 ppm would mean (derived from the 2010 NOAA-led
report):
The Hadley Center has a huge but useful figure which I will reproduce here:
Note again that this is not the worst-case scenario. It’s just business as usual out to 2100.
In the worst case, we get both continuing high levels of emissions and high carbon-cycle feedbacks. That possibility was discussed here:
This would be the worst-case for the 2060s, but is in any case, close to business as usual for 2090s:
This is a staggering 13-18°F over most of U.S. and 27°F in the Arctic.
And there is every reason to believe that the earth would just keep getting hotter and hotter:
Steve Easterbrook’s
post “A first glimpse at model results for the next IPCC assessment” shows that for the scenario
where there is 9°F warming by 2100, you get another 7°F warming by 2300.
Of course, folks that aren’t motivated to avoid the
civilization-destroying 9°F by 2100 won’t be moved by whatever happens
after that.
DUST-BOWL-IFICATION
The Palmer Drought Severity Index (PDSI)
in the 2060s and 2090s in a moderate emissions path. A ”reading of -4 or
below is considered extreme drought.”
The PDSI in the Great Plains during the
Dust Bowl apparently spiked very briefly to -6, but otherwise
rarely exceeded -3 for the decade (see
here). The study finds:
The large-scale pattern shown in Figure
11 [of which the figure above is part]
appears to be a robust response to increased GHGs. This is very alarming because if the drying is anything resembling Figure
11,
a very large population will be severely affected in the coming decades
over the whole United States, southern Europe, Southeast Asia,
Brazil, Chile, Australia, and most of Africa.
The National Center for Atmospheric Research notes “By the end of the century, many
populated areas, including parts of the United States and much of he
Mediterranean and Africa, could face readings in the range of -4 to
-10. Such decadal averages would be almost unprecedented.”
For the record, the NCAR study merely models the IPCC’s “moderate”
A1B scenario — atmospheric concentrations of CO2 around 520 ppm in
2050 and 700 in 2100. We’re currently headed much higher by century’s
end, but I’m sure with an aggressive program of energy R&D we
could keep that to, say 800 ppm.
- The UK Met Office came to a similar view six years ago in their analysis, projecting severe drought over 40% of the Earth’s habited landmass by century’s end (see “The Century of Drought“).
- A 2012 Nature Climate Change article, “Increasing drought under global warming in observations and models” (subs. req’d, news release here)
confirms these findings, concluding, “the observed global aridity
changes up to 2010 are consistent with model predictions, which suggest
severe and widespread droughts in the next 30–90 years over
many land areas resulting from either decreased precipitation and/or
increased evaporation.” In particular, the author has a stunning warning for this country: “The U.S. may never again return to the relatively wet conditions experienced from 1977 to 1999.”
The projection of extended if not endless drought for the US
Southwest (and parts of the Great Plains) has been studied a great deal:
The serious hydrological changes and impacts known to
have occurred in both historic and prehistoric times over North America
reflect large-scale changes in the climate system that can develop
in a matter of years and, in the case of the more severe past
megadroughts, persist for decades. Such hydrological changes fit the
definition of abrupt change because they occur faster than the time
scales needed for human and natural systems to adapt, leading to
substantial disruptions in those systems. In the Southwest,
for example, the models project a permanent drying by the mid-21st
century that reaches the level of aridity seen in historical droughts,
and a quarter of the projections may reach this level of aridity
much earlier.
An unprecedented combination of heat plus decades of drought could be in store for the Southwest sometime this century, suggests new research from a University of Arizona-led team”….
“The bottom line is, we could have a Medieval-style drought with even warmer temperatures,” [lead author Connie] Woodhouse said.
- A 2011 Environmental Research Letters article, “Characterizing changes in drought risk for the United States from climate change,”
comes to a similar conclusion as the NCAR study, “Drought
frequencies and uncertainties in their projection tend to increase
considerably over time and show a strong worsening trend along higher
greenhouse gas emissions scenarios, suggesting substantial benefits
for greenhouse gas emissions reductions.” See especially Figure 4C.
Again, this is all just business as usual.
Finally, the heat and drought drives wildfires. Here’s a National Academies figure from a
presentation made by the President’s science adviser Dr. John Holdren in Oslo in 2010, about conditions projected for mid-century:
SEA LEVEL RISE
A dozen major studies since the IPCC report have concluded that we face much higher sea level rise this century:
Four studies in 2012 provide yet more cause for concern
- Three new Studies on Sea Level Rise Make Clear We Must Act Now.
Staying near our current greenhouse emissions emissions path — not the
worst-case scenario — still leads to over 40 inches of sea level rise
by 2100 and then seas continue to rise 7 inches or more a decade!
- Sea Level Rise: It Could Be Worse Than We Think:
“Seas could rise dramatically higher over the next few centuries than
scientists previously thought — somewhere between 18-to-29 feet above
current levels, rather than the 13-to-20 feet they were talking about
just a few years ago.”
Needless to say, a sea level rise of one meter by 2100 (nearly 40
inches) would be an unmitigated catastrophe for the planet, even if sea
levels didn’t keep rising several inches a decade for centuries, which
they inevitably would. The first meter of SLR would flood
17% of Bangladesh,
displacing tens of millions of people, and reducing its rice-farming
land by 50 percent. Globally, it would create more than 100 million
environmental refugees and inundate
over 13,000 square miles of this country. Southern Louisiana and South Florida would inevitably be abandoned.
SPECIES LOSS ON LAND AND SEA
Many more studies have raised similar concerns:
As for the worst-case scenario, we have:
Yes, some scientists disputed the analysis, but I have seen no refutation in the scientific literature.
UNEXPECTED IMPACTS
If we go to 800 ppm — let alone 1000 ppm or higher — we are far
outside the bounds of simple linear projection. Some of the worst
impacts may not be obvious — and there may be unexpected negative
synergies. The best evidence that will happen is the fact that it is
already happened with even a small amount of warming we have seen to
date.
… the cumulative impact of the beetle outbreak in the affected region during 2000–2020 will be 270 megatonnes (Mt) carbon (or 36 g carbon m-2 yr-1 on average over 374,000 km2 of forest). This impact converted the forest from a small net carbon sink to a large net carbon source.
No wonder the carbon sinks are saturating faster than we thought (see
here) — unmodeled impacts of climate change are destroying them:
Insect outbreaks such as this represent an
important mechanism by which climate change may undermine the ability of
northern forests to take up and store atmospheric carbon, and such impacts should be accounted for in large-scale modelling analyses.
The key point is this catastrophic climate change impact and
its carbon-cycle feedback were not foreseen even a dozen years ago —
which suggests future climate impacts will bring other equally
unpleasant surprises, especially as we continue on our path of no
resistance.
EXTREME WEATHER
One of the basic predictions of climate science is that extreme
weather will make the hydrological cycle more extreme. I’ve already
discussed the extensive (and growing) literature on how dry areas will
get drier. But wet areas will also get wetter:
1) Here we show that human-induced increases in
greenhouse gases have contributed to the observed intensification of
heavy precipitation events found over approximately two-thirds of
data-covered parts of Northern Hemisphere land areas. These
results are based on a comparison of observed and multi-model simulated
changes in extreme precipitation over the latter half of the twentieth
century analysed with an optimal fingerprinting technique.
Changes in extreme precipitation projected by models, and thus the
impacts of future changes in extreme precipitation, may be
underestimated because models seem to underestimate the observed
increase in heavy precipitation with warming.
2) Occurring during the wettest autumn in England and Wales since records began in 1766 these
floods damaged nearly 10,000 properties across that region, disrupted
services severely, and caused insured losses estimated at £1.3
billion….
… it is very likely that global anthropogenic greenhouse
gas emissions substantially increased the risk of flood occurrence in
England and Wales in autumn 2000.
That post ended with its own review of the literature on the
connection between global warming and extreme weather. Here are several
more recent studies on how warming is already making our weather more
extreme:
A new study by a Duke University-led team of climate scientists suggests that
global warming is the main cause of a significant intensification in
the North Atlantic Subtropical High (NASH) that in recent decades has
more than doubled the frequency of abnormally wet or dry summer
weather in the southeastern United States….
The models – known as Coupled Model Intercomparison Project Phase 3 (CMIP3) models –
predict the NASH will continue to intensify and expand as
concentrations of carbon dioxide and other greenhouse gases increase in
Earth’s atmosphere in coming decades.”This
intensification will further increase the likelihood of extreme summer
precipitation variability – periods of drought or deluge – in
southeastern states in coming decades,” Li says.
The team calculates that a 1 ºC increase in
sea-surface temperatures would result in a 31% increase in the global
frequency of category 4 and 5 storms per year: from 13 of those storms
to 17. Since 1970, the tropical oceans have warmed on average by around
0.5 ºC. Computer models suggest they may warm by a further 2 ºC by
2100.
- Nature: Strong Evidence Manmade ‘Unprecedented Heat And Rainfall Extremes Are Here … Causing Intense Human Suffering’
- Hansen et al: “Extreme Heat Waves … in Texas and Oklahoma in 2011 and Moscow in 2010 Were ‘Caused’ by Global Warming”
- Study Finds 80% Chance Russia’s 2010 July Heat Record Would Not Have Occurred Without Climate Warming
- NOAA: Human-Caused Climate Change Already a Major Factor in More Frequent Mediterranean Droughts
The very latest science suggests we may actually be in the midst of a
quantum leap or step-function change in extreme weather because of
warming-driven Arctic ice loss:
FOOD INSECURITY
Population growth, dietary shifts, growing use of crops for biofuels,
peaking conventional oil production and increases in extreme weather
have all played a part. As the literature above makes clear, on our
current emissions path, we face:
Further modeling the impact of warming-driven extreme weather shocks lead
Oxfam to conclude corn prices could increase a staggering 500% by 2030:
The “additional price increase” percentage (olive green bars) is calculated off the original price increase.
DIRECT HEALTH IMPACTS

In 2011 the
British Medical Journal
warned that climate change “poses an immediate and grave threat,
driving ill-health and increasing the risk of conflict, such that each
feeds upon the other.” The UK’s Hadley Center
notes that on our current one related impact, “
By
the 2090s close to one-fifth of the world’s population will be
exposed to ozone levels well above the World Health Organization
recommended safe-health level.”
A just-released September 2011 report by the European Lung Foundation finds:
Scientists are warning that death rates linked to climate change will
increase in several European countries over the next 60 yrs.
Earlier this year, Climate Progress reported on what the top medical and health groups warn are the
health risks Americans face from climate change:
- More than doubled asthma rates and lengthened asthma season (already 20 days longer)
- Threatened access to clean drinking water
- Increases in airborne and insect borne illnesses (e.g. mosquitos, ticks, tapeworm)
- Increases in diarrheal, respiratory, and heart disease
- Increased risk of salmonella spread as average temperatures rise
- Increase in hospital use results in rising health care costs
- Particular risk among low-income communities, children, the elderly, and the obese
CONCLUSION
The possibility that unrestricted emissions of greenhouse gases would
not do unimaginable harm to humanity has become vanishingly small.
That’s because:
- We remain near the worst-case emissions pathways
- There is little prospect of major national or global action any times soon (thank you, deniers)
- Many impacts are coming faster than the models projected, and
- The overwhelming majority of the scientific literature in the past 5
years has been more dire than the 2007 IPCC report, which itself was
more than enough motivation for the overwhelming majority of climate
scientists and countries to call for urgent action to reduce emissions.
And I haven’t even discussed the many, many studies that suggest in
fact carbon-cycle feedbacks (like the defrosting tundra) are almost all
positive (amplifying) and yet largely ignored in most climate models:
- NSIDC:
Thawing permafrost feedback will turn Arctic from carbon sink to
source in the 2020s, releasing 100 billion tons of carbon by 2100 and
links therein.
- Nature: Climate Experts Warn Thawing Permafrost Could Cause 2.5 Times the Warming of Deforestation!
- Forest Feedback: Rising CO2 In Atmosphere Also Speeds Carbon Loss From Forest Soils, Research Finds
- For Peat’s Sake: Record Temperatures And Wildfires In Eastern Russia Drive Amplifying Carbon-Cycle Feedback
- Stunning Peatlands Amplifying Feedback: Drying Wetlands and Intensifying Wildfires Boost Carbon Release Ninefold
- Carbon Feedback From Thawing Permafrost Will Likely Add 0.4°F – 1.5°F To Total Global Warming By 2100
So it’s no surprise that many climate impacts are coming much faster than the models had predicted:
Arctic Sea Ice is melting much, much faster than even
the best climate models had projected. The reason is most likely
unmodeled amplifying feedbacks. Image via Arctic Sea Ice Blog.
Inaction means humanity’s self-destruction. We must pay any price or bear any burden to stop catastrophic climate change.