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Study Concludes 10 More Years of Business-as-Usual CO2 Emissions Could Make Avoiding Dangerous Climate Change Impossible
30 May 2007
An additional 10 years of continued rapid growth of CO2 emissions and infrastructure may make avoiding dangerous climate change “impractical, if not impossible”, according to a recently published study in the journal Atmospheric Chemistry and Physics.
The lead author of the study is James Hansen, Director of NASA’s Goddard Institute for Space Studies (GISS) in New York. Forty-six other researchers from other organizations in the US and France also contributed to the work. The researchers used data from earlier warm periods in the Earth’s history to estimate climate impacts as a function of global temperature, climate models to simulate global warming, and satellite data to verify ongoing changes.
Although identifying “dangerous” effects is “partly subjective”, the report concludes that additional global warming of more than 1°C above the level in 2000 will have effects that may be highly disruptive, and push the climate past tipping points.
Tipping points can occur during climate change when the climate reaches a state such that strong amplifying feedbacks are activated by only moderate additional warming. This study finds that global warming of 0.6°C in the past 30 years has been driven mainly by increasing greenhouse gases, and only moderate additional climate forcing is likely to set in motion disintegration of the West Antarctic ice sheet and Arctic sea ice. Amplifying feedbacks include increased absorption of sunlight as melting exposes darker surfaces and speedup of iceberg discharge as the warming ocean melts ice shelves that otherwise inhibit ice flow.
Have we already passed a “tipping point” such that it is now impossible to avoid “dangerous” climate change? In our estimation, we must be close to such a point, but we may not have passed it yet. It is still feasible to achieve a scenario that keeps additional global warming under 1°C, yielding a degree of climate change that is quantitatively and qualitatively different than under BAU scenarios.
The researchers conclude that a CO2 level exceeding about 450 ppm would be dangerous. The current atmospheric concentration of CO2 is currently 383 ppm, up from 280 ppm at the start of the industrial age. Atmospheric carbon is currently increasing at about 2 ppm per year.
The study also shows that the reduction of non-carbon dioxide forcings such as methane and black soot can offset some CO2 increase, but only to a limited extent.
The team used a computer model developed by the Goddard Institute to simulate climate from 1880 through today. The model included a more comprehensive set of natural and human-made climate forcings than previous studies, including changes in solar radiation, volcanic particles, human-made greenhouse gases, fine particles such as soot, the effect of the particles on clouds and land use. Extensive evaluation of the model’s ability to simulate climate change is contained in a companion paper to be published in Climate Dynamics.
The authors use the model for climate simulations of the 21st century using both business-as-usual growth of greenhouse gas emissions and an alternative scenario in which emissions decrease slowly in the next few decades and then rapidly to achieve stabilization of atmospheric CO2 amount by the end of the century. Climate changes are so large with business-as-usual, with additional global warming of 2-3°C (3.6-5.4°F) that Hansen concludes “business-as-usual would be a guarantee of global and regional disasters.”
However, the study finds much less severe climate change—one-quarter to one-third that of the business-as-usual scenario—when greenhouse gas emissions follow the alternative scenario.
A scenario that avoids “dangerous” climate change appears to be still technically feasible.
Our conclusion that global temperature is nearing the level of dangerous climate effects implies that little time remains to achieve the international cooperation needed to avoid widespread undesirable consequences. CO2 emissions are the critical issue, because a substantial fraction of these emissions remain in the atmosphere “forever”, for practical purposes. The principal implication is that avoidance of dangerous climate change requires the bulk of coal and unconventional fossil fuel resources to be exploited only under condition that CO2 emissions are captured and sequestered.
A second inference is that remaining gas and oil resources must be husbanded, so that their role in critical functions such as mobile fuels can be stretched until acceptable alternatives are available, thus avoiding a need to squeeze such fuels from unconventional and environmentally damaging sources. The task is to achieve a transition to clean carbon-free energy sources, which are essential on the long run, without pushing the climate system beyond a level where disastrous irreversible effects become inevitable.
Separately, a different new study by NASA scientists suggests that business-as-usual greenhouse-gas warming may raise average summer temperatures in the eastern United States nearly 10° Fahrenheit by the 2080s. It also suggests that current climate models are underestimating surface temperature changes.
The research found that eastern US summer daily high temperatures that currently average in the low-to-mid-80s (degrees Fahrenheit) will most likely soar into the low-to-mid-90s during typical summers by the 2080s. In extreme seasons—when precipitation falls infrequently—July and August daily high temperatures could average between 100 and 110 degrees Fahrenheit in cities such as Chicago, Washington, and Atlanta.
To reach their conclusions, the researchers analyzed nearly 30 years of observational temperature and precipitation data and also used computer model simulations that considered soil, atmospheric, and oceanic conditions and projected changes in greenhouse gases. The simulations were produced using a widely-used weather prediction model coupled to a global climate model developed by NASA’s Goddard Institute for Space Studies.
The global model, one of the models used in the recently issued climate report by the Intergovernmental Panel on Climate Change (IPCC), was utilized in this study to identify future changes in large-scale atmospheric circulation patterns due to the build up of greenhouse gases. This information was then fed into the weather prediction model to forecast summer-to-summer temperature variability in the eastern United States during the 2080s. The weather model showed that extreme summertime surface temperatures developed when carbon dioxide emissions were assumed to continue to increase about two percent a year, the “business as usual” scenario. These findings are too recent to be included in the latest IPCC report.
The weather prediction model used in this research is advantageous because it assesses details about future climate at a smaller geographic scale than global models, providing reliable simulations not only on the amounts of summer precipitation, but also on its frequency and timing. This is an important capability for predicting summer temperatures because observed daily temperatures are usually higher on rainless days and when precipitation falls less frequently than normal.
The study determined that the global climate model (GCM) likely underestimates future air temperatures near the ground because it simulates too many rainy days on which clouds block sunlight and on which the wet ground is additionally cooled by evaporation. Statistics of rain frequency inherently depend on the size of the area being monitored, since it rains more often somewhere within a large area than somewhere within a much smaller area. The smaller area of the weather prediction model provided better tuning.
However, even accounting for the relatively large area of the GCM's computational elements, the NASA researchers found that the GCM still overestimates precipitation frequency. By comparison, the corresponding percentage of rainy days predicted by the regional mesoscale model for the same summers was lower and much more realistic.
The scientific literature indicates that other GCMs are also flawed by computations of too frequent precipitation and unrealistic morning showery precipitation. We are not aware of any other study that has documented the impact of the precipitation simulation imperfections on GCMs’ predictions of surface air temperature, but the ability of such flawed models to predict global warming and its extremes could be compromised. This study suggests that climate change will cause more extreme temperatures than implied by previous GCM studies.
(A hat-tip to Marcus!)
Resources:
“Dangerous human-made interference with climate: a GISS modelE study”; J. Hansen, M. Sato, R. Ruedy, P. Kharecha, A. Lacis, R. Miller, L. Nazarenko, K. Lo, G. A. Schmidt, G. Russell, I. Aleinov, S. Bauer, E. Baum, B. Cairns, V. Canuto, M. Chandler, Y. Cheng, A. Cohen, A. Del Genio, G. Faluvegi, E. Fleming, A. Friend, T. Hall, C. Jackman, J. Jonas, M. Kelley, N. Y. Kiang, D. Koch, G. Labow, J. Lerner, S. Menon, T. Novakov, V. Oinas, Ja. Perlwitz, Ju. Perlwitz, D. Rind, A. Romanou, R. Schmunk, D. Shindell, P. Stone, S. Sun, D. Streets, N. Tausnev, D. Thresher, N. Unger, M. Yao, and S. Zhang; Atmos. Chem. Phys., 7, 2287–2312, 2007
“An analysis of the potential for extreme temperature change based on observations and model simulations”; Lynn, B.H., R. Healy, and L.M. Druyan; J. Climate, 20, 1539-1554, doi:10.1175/JCLI4219.1.
Precipitation and the Potential for Extreme Temperature Change (NASA Science Brief)
May 30, 2007 in Climate Change | Permalink | Comments (144) | TrackBack (0)
Comments
Posted by: Andrey | May 30, 2007 at 10:37 PM
Richard:
The only thing I am trying to tell is quite simple: there is NO tipping point for runaway global warming due to GHG. It is confirmed by wide variations of CO2 in atmosphere, in dozens of both cold and hot periods, during thousands and millions years of Earth history. Earth never melted down and always returned back from hot periods and extremely high CO2 back to “normal”. If climate models do not agree with this, they are WRONG.
Posted by: Andrey | May 30, 2007 at 10:50 PM
Andrey, you and anyone else can always pull some bit of data out from somewhere and claim it proves something. This is why there are still creationists and this is why there are still many lay people who believe the type of climate commentary you write.
When we get serious about information though we have a peer review process in which scientists in the field assess submitted papers to journals. Only scientists in the field have the background knowledge that enables them to assess whether someone is cherry picking or not etc etc.
If you really had a valid point you could submit an article to a scientific publication and have it assessed by professionals. At the very least you should be able to point us to discussions that you should have had over at realclimate with people of suitable background. Unless you do any of this there is simply no reason not to ignore you.
Posted by: marcus | May 30, 2007 at 11:15 PM
Andrey is referring to an old controversy about lower troposphere cooling indicated by satellite measurements. This has been resolved in quite different way than Andrey indicates. Satellite measurements were wrong, since they had made wrong corrections to take thethe slowing down of satellites into account. New data sets show warming of lower troposphere as should be expected when surface temperatures have been warming. See for yourself:
http://environment.newscientist.com/channel/earth/climate-change/dn11660
and in more detail at
http://www.climatescience.gov/Library/sap/sap1-1/finalreport/default.htm
Posted by: jk | May 31, 2007 at 12:03 AM
Stop arguing guys, its time to launch a solar shield satelite to block off some of those evil sunlight and we will have global cooling!
Posted by: rexis | May 31, 2007 at 12:57 AM
Even more simple (and cheap) solution to reduce solar heating:
Paint the deserts white.
Posted by: clett | May 31, 2007 at 03:04 AM
For daily updated news on biofuels, ethanol and climate change issues, please visit:
http://www.ethanol-news.de
Posted by: Marian | May 31, 2007 at 03:20 AM
Andrey is right that half a billon years ago atmospheric CO2 was much higher than it is today and yet the world had temperatures that could sustain complex animals. He does not give a source (I would like one Andrey) but here is one http://www.spaceref.com/news/viewpr.html?pid=12577 . However, the conclusion made by Andrey that we should therefore not worry about GW and not pay attention to the findings of the GW scientists is wrong because it is based on ceteris paribus. The source I give say that the sun was emitting far less heat hundred of million of years ago and therefore the world would have been much colder and possible inhabitable so if it had not been for the extra greenhouse gasses in the atmosphere at that time.
Catastrophic is a very subjective word that is perceived differently from human to human. It is a fact that right now the temperature increases caused by GW are already decimating many species and extinguishing many more that simply are unable to adapt fast enough to survive the increasing temperatures. It is a fact that human activity including GW is eliminating many times more spices than the Mother Nature is able to create considering the same time period. Global biodiversity decreases dramatically these years because of human activity notably GW. This is in my subjective opinion already catastrophic enough to warrant big time action immediately. That we now face a deteriorating situation that may possibly result in a planet that is inhabitable to complex animals like humans is even more catastrophic. Obviously any rationally minded person would say that this scenario is not worth risking for any saved money no matter how small the probability.
Do something if you possibly can. GW is much bigger and far more important and damaging than global terrorism.
Posted by: Henrik | May 31, 2007 at 04:57 AM
Sorry just saw the sun radiation point was already made.
Posted by: Henrik | May 31, 2007 at 05:08 AM
The thing is, GCMs that illustrate our dire situation have been coming out for years; yet nothing has changed! Opponents of GW aren't going to be swayed by GCMs because they are never going to be 100% accurate. Just as long as there is 1% chance that model will fail, opponents will cling to that 1%. The vast majority of scientific fact already supports GW, so perhaps it's time to look outside of science to convince these nay-sayers.
Posted by: gnoble | May 31, 2007 at 05:50 AM
Can someone please post a few links to show where the idea that scientists are making millions by promoting global warming is coming from? I'm looking for something that is more about specific cases rather than grandiose statements. I really want to know if there is indeed a profit motive for these scientists and organizations.
It is clear that there is substantial profit motive for those who believe that global warming is a hoax, or at least put forth that public position. This is an inarguable fact.
But I'm totally open to the idea that there are people who have figured out how to work the system from the other side.
Posted by: Wanderer | May 31, 2007 at 05:53 AM
Funny,
you can barely get a half decent weather forecast for tomorrow. The forecast for next week is outright unreliable (Try tracking the forecast for a particular date at weather.com for a week, you will see a different forecast for the same date almost every day). Climatologists can not predict in a reliable manner whether this summer will be hot or next winter will be cold (how many unexpected El Nino's have we seen in the last 15 years?), but they are able to predict the climate several decades ahead? Please.
Posted by: Petroleo | May 31, 2007 at 05:53 AM
Global warming is but 1 reason to get off oil. Why the constant bickering about it? Peak oil and our suibsidizing Arab governments and the related terrorism are just as valid if not more valid reasons we have to do something about our overconsumption of oil. Don't believe in AGW? Fine by me! But are you saying we shouldn't start to reverse the trend of increasing oil demand? Are the solutions to the problem any different wether you come from an AGW concern or a national security concern? Not really! Why can't people let others have their own reasons fro change and let's get working on actually doing something instead of wasting time on the reasons.
Posted by: darwin | May 31, 2007 at 06:17 AM
Relax Darwin,
getting off of oil for the reasons you mentioned makes a lot of sense, and I'm all for it. But let's just call a spade a spade shall we? Makes the discussion much more rational. And if you do want to believe in man made global warming, be my guest, just don't expect me to join the hype of the day. And just to note, you didn't have any argument against my little discours did you?
Posted by: Petroleo | May 31, 2007 at 06:42 AM
One quick note to add to the discussion. Several folks keep refering to what happened over the last 'millions' of years or so. No one is disputing that what is happening now has not happened before. After all - the carbon that we are emitting at one time was in the atmosphere. However, the issus is the amount of time in which the change to climate is predicted. This is not a matter of dispute. (unless you desire to dispute the entire notion of the scientific method)
The impact of a few degree centigrade temperatur change over a 50 year period pretty much sucks for life that is used to having thousands of years to adapt to new climate.
Posted by: Eric S | May 31, 2007 at 06:54 AM
Part of the problem is that people confuse the 'latest research' with 'scientific knowledge'. The peer review process is a fine thing, don't get me wrong, but all it does is ensure that a paper has met a minimum standard of rigor and logic - it doesn't mean that the paper's conclusions are in any way correct.
Papers that have passed the review process and are published are often refuted or discredited later on - one of the best ways to establish your credibility as a researcher is to do just that. It's only after the conclusions have stood the test of time that they should be considered as part of scientific canon.
Most of these spectacular conclusions ("We have only ten years left!" "No, it's twenty!" "It's five! We're all gonna die!") have a long ways to go before reaching that standard.
(And yes, I fully appreciate the irony of urging patience regarding predictions of short-term doom.)
Posted by: Matthew | May 31, 2007 at 07:07 AM
A note about weather forecast vs climate prediction:
To talk about the inability to predict weather for a specific city one week to the next - or even to be able to predict an extreme of a particular season for a region is asking a science that is based on historical trends to deliver predictive forcasting.
In the last 20 years weather forecasts have become alarmingly accurate. Some times so much so that I am hoping they are wrong - only to be soaked while on the golf course. Think about how difficult it is to compare past weather behavior and predict an outcome.
Another perspective of this: Think about this from a statisitical referece. It is easy to predict long-term trend changes based upon extensive hitorical data altered with minute changes in constraints. However, try to use the same data to predict a particular day stock high - and you will fail. Past performance does not always predict future results. This is because of the number and variety of constraints - some of which are nearly impossible to identify.
Posted by: Eric S | May 31, 2007 at 07:20 AM
If anyone here has a problem with the model, go through it an tell us exactly where the model has gone wrong. In the mean time, we need to do everything possible to cut our carbon emissions.
Part of what is required is to pretty much shut down the use of the automobile, except for those autos that are running on low carbon or zero carbon energy. If that means we cut our vehicle miles traveled by at least 80%, so be it. Even if global warming did not exist, the world would be a much better, pleasant, cleaner, healthier, safer place without it.
The auto, of course, is just one part of the puzzle.
Do our leaders have the stones and the vision to do anything about the problem. Sadly, it would appear, no.
Posted by: tom | May 31, 2007 at 07:38 AM
Anyone? Please post a link or two as per my request.
I do have another concern. Those who say that human out-gassing of C02 is too negligible to effect the climate. How come, when you plug in the amount of C02 we have emitted into climate simulators, starting with 1800 and moving forward, do they all seem to show the C02 having a very real effect? Can they all be wrong?
I know that since the late 70's, when computing power started to really do the Moore's Law thing, all models have shown the same thing to varying degrees. None of them showed that human out-gassing of C02 had no effect.
As Moore's Law has given us tools that are many, many orders of magnitude greater than what we had even 10 years ago, and they are still showing the same thing, how can any rational person disagree with them? This is baffling. Absolutely baffling and terrifying.
Posted by: Wanderer | May 31, 2007 at 07:47 AM
Quote: "Climatologists can not predict in a reliable manner whether this summer will be hot or next winter will be cold (how many unexpected El Nino's have we seen in the last 15 years?), but they are able to predict the climate several decades ahead? Please." -Petroleo
Extreme climate variability is evidence of changing climate patterns. If you want to believe human sources of CO2 are not part of the cause for those changing climate patterns, you have that option. But that does not change the fact that climate change is occurring.
To address the "millions of years ago there was more CO2" argument, let me stress the importance of understanding rates of change. Natural climate cycles and CO2 levels change very slowly (historically). Human-caused increases in atmospheric CO2 have occurred at unprecedented rates of change. The elasticity of the climate has been stretched by this extremely rapid change. I am personally concerned about any naturally corrective climate behaviors in the future. The "snap-back" effect of the climate could be very detrimental to civilization on this planet.
Posted by: Culprititus | May 31, 2007 at 07:48 AM
I can't tell you what is wrong with the climate models Tom, I'm not a climatologist. But I know I can't trust the weatherman, at least not where I live, in north western europe. Probably in the Sahara desert it is easier to predict the weather. If we are going to take the kind of action you propose, we should better damn well know what were doing and why. I'm definitely not against the car, and I don't believe life would be better without it. I would like mine to use less gasoline though, if possible none, and not make any noise or emit fumes, which is why is visit this site.
Posted by: Petroleo | May 31, 2007 at 07:51 AM
Climate has always been changing, and it will always be changing. The earth has gone from being completely covered with ice to be being completely ice free, passing thorugh through every stage in between. There sure weren't any coal fired powerstations or SUV's for most of earths history. Yes the climate is changing, I also notice winters being warmer than 25 years ago. Someone else here said past results are no indication for the future. Well that is exactly my point: It has indeed been getting warmer, but what does that tell us about the future? Not very much in my view. So why should we base policy on something that we don't know, instead of basing it on things we do know, like dwindling oil reserves, geopolitical concerns with respect to energy security and so on? Does the climate lobby want to win the Donald Rumsfeld trophy?
Posted by: Petroleo | May 31, 2007 at 08:01 AM
Petroleo, please see my post and respond.
Or, let me rephrase:
If climate models since the 1970's have all shown that human out-gassing of C02 does warm the earth's climate, why do you not find this compelling?
Remember, everything is based on reasonable doubt, there are no certainties or absolutes. At some point we have to make decisions based on the best information we have at the time. Or, we wait until it is a past event.
Posted by: Wanderer | May 31, 2007 at 08:10 AM
Because models are just that: models. They're someones assumptions expressed as mathematical equations retrofitted on historical obervational data, and then extrapolated into the future. One could do the same excercise on the historical values of the Dow Jones and try to predict the future behavior of the stock exchange. O wait, that is in fact being done by hedge fund managers. And it will work as long as it will work, until it won't, and then they loose a lot of money, like LCTM in 1998. The point is the models are as good as the assumptions and the data. And we have historical records for the Dow Jones for a longer period than for global satellite temperature data. The only thing these models really prove is that at Nasa they have some excellent computer programmers.
Posted by: Petroleo | May 31, 2007 at 08:25 AM
No, maybe I was not clear.
Currently, we are able to look back in time, know the exact amount of C02 actually out-gassed, how much the earth temp as increased, plug it into models from the 1970's, and they predict the same basic amount of temp increase that we actually have.
Plug in the same known data (it is past, so it is fact) into any climate model from any year in the past, they show the same. Sure, there is some variance, but the one thing they all show is a temp increase caused by the C02 out-gassed.
So at what point does using past models with known past data and having them correlate to what has already occurred, does this give us enough information to take action? Like I said, either you make a decision based on the best information at the time, or you wait until it has already happened.
Posted by: Wanderer | May 31, 2007 at 08:51 AM
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Cervus:
Junkscience just presents officially issued numerical data in convenient graph form with overlay of CO2 concentrations. Their graphs are universally used by scientists in many climate blogs. But you can find satellite records everywhere, for example here:
http://science.nasa.gov/NEWHOME/headlines/essd06oct97_1.htm
http://www.warwickhughes.com/blog/?p=28
(MSU graph is satellite measurements)
http://clima.ictr.pd.cnr.it/microclima/sturaro/MSU/MSUintro2.html