Climate scientists see better climate models, warmer future

Sep 30, 2013 by Julie Chao
Berkeley Lab scientists Michael Wehner (left) and William Collins were lead authors on the IPCC Fifth Assessment Report. Credit: Roy Kaltschmidt/Berkeley Lab

(Phys.org) —Over the next century, most of the continents are on track to become considerably warmer, with more hot extremes and fewer cold extremes. Precipitation will increase in some parts of the world but will decrease in other parts. These are some of the conclusions reached by Lawrence Berkeley National Laboratory (Berkeley Lab) scientist Michael Wehner and his co-authors on the Fifth Assessment Report of the Intergovernmental Panel on Climate Change (IPCC).

Wehner, a scientist in Berkeley Lab's Computational Research Division, and William Collins, head of the Lab's Climate Sciences Department, were lead authors on the IPCC report's chapters on long-term climate change projections and climate models, respectively. They are among more than 200 lead authors from more than 30 countries in IPCC's Working Group I. Their report released today provides a comprehensive assessment of the physical science basis of climate change.

The rest of the Fifth Assessment Report, from Working Groups II and III, which also include contributions from several other Berkeley Lab scientists, will be released next spring. IPCC's Fourth Assessment Report, released in 2007, and which Collins and more than a dozen other Berkeley Lab researchers worked on, helped it win the 2007 Nobel Peace Prize, shared with Al Gore.

As in the previous report, Collins worked with an international team of climate scientists tasked with evaluating the physical fidelity of the climate models used in the IPCC's assessment. He noted that both the quantity and quality of climate models have increased significantly in the last six years. Processes such as cloud formation and rain formation are now better understood and better represented in .

"The models are far more complete," Collins said. "Also their resolution has increased dramatically. We're able to start to resolve regional climate change in greater detail."

While there is still some scientific uncertainty around how sensitive the climate is to carbon dioxide in the atmosphere, Collins stresses that the fundamental conclusion reached by climate scientists more than 20 years ago remains unchanged. "Increased fidelity of the models is not altering the underlying conclusion, that increased carbon dioxide will lead to dramatic changes in our climate," he said. "We have very high confidence that the models are simulating the key features in the earth's climate."

Using climate model results provided by the international scientific community, Wehner worked with other report lead authors to make long-term projections of changes in average and extreme temperature, precipitation and other aspects of the moisture cycle at the end of this century compared to the end of the last century. Their main finding? "The rare event becomes commonplace," Wehner said. "We are virtually certain that as the overall climate warms there will be more hot days and fewer colder nights."

These projections are under the so-called "no-policy scenario," which was one of several scenarios the scientists made projections for. It assumes that the world population and economy continue to grow but no policies are put in place to mitigate emissions of climate-warming gases, such as carbon dioxide. "The no-policy scenario is the worst case we considered," Wehner said. "It is not the worst-case scenario."

The rosiest scenario considered was the so-called geoengineering scenario. "Some call that the vacuum-cleaner scenario, because we have to invent a technology to clean CO2 out of the atmosphere as well as reduce our emissions dramatically, so as to actually have negative emissions of greenhouse cases," he said. "Even in this case, the average temperature will be nearly 2 degrees (centrigrade) higher than it was before industrialization."

As for precipitation, certain areas will be drier and others will see more rainfall, snow and storms, especially in the winter and spring seasons. Extremely heavy precipitation is projected to very likely become more extreme in a warmer world. Somewhat paradoxically, intensities and durations of future drought are likely to become more severe.

The scientists also considered several scenarios between the two extremes of no policy and geoengineering. "The intermediate scenarios gave intermediate results," Wehner said. "These four scenarios are meant to inform policymakers of the consequences of their choices."

Other Berkeley Lab scientists who contributed to this report were William Riley of the Earth Sciences Division and Prabhat of the Computational Research Division.

Explore further: Newly released climate change report reinforces need for action

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wombatmobile
2.1 / 5 (7) Oct 01, 2013
Why do we have so many different "models"? If we know how to model Earth's climate, there should only be one definitive model. Averaging the models is pseudoscience! It is like averaging the horoscopes.

If the models were accurate simulations of Earth's climate, we could test them by setting the initial conditions to any year in the past, running 100 years of simulation, and then comparing the results to the actual recorded data of Earth's climate during the period. The problem with the models is that they are only "accurate" for the few decades for which they are calibrated e.g. 1980 - 2010. The same models don't work for 2000 BC - 1900 BC, or 200,000 BC - 199,900 BC. For that reason, the models are not accurate models of Earth's climate. They are just equations that link today's atmospheric carbon to 2030's temperature in a way that suits global warming proponents.
ekim
3.7 / 5 (6) Oct 01, 2013
Don't we use computer models for other situations? Would you expect them to have only one definite outcome or model?
http://en.wikiped...mulation
You should educate yourself before posting.
runrig
3.7 / 5 (6) Oct 01, 2013
Why do we have so many different "models"? If we know how to model Earth's climate, there should only be one definitive model. Averaging the models is pseudoscience! It is like averaging the horoscopes.


If you think it is pseudoscince then I would suggest you are woefully ignorant of computer modeling of weather/climate and as such should not reveal it.
It is for the same reason Meteorologists run "ensembles" - to get a handle on the chaos in the system and develop confidence levels. The models in various centres around the world produce slightly different results and highlight areas of possible difficulty and development of the system.

If the models were accurate simulations of Earth's climate, we could test them by setting the initial conditions to any year in the past, running 100 years of simulation, and then comparing the results to the actual recorded data of Earth's climate during the period.


Err.... THEY DO .... !!.

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