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

( —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

add to favorites email to friend print save as pdf

Related Stories

UN report to point to mounting climate challenge

Sep 21, 2013

Scientists will hike pressure next week on the UN's troubled climate talks as they release a report pointing to the dizzying challenge of meeting the international body's target for global warming.

Climate panel forecast: Higher seas, temperatures

Sep 28, 2013

Top scientists have a better idea of how global warming will shape the 21st century: In a new report, they predict sea levels will be much higher than previously thought and pinpoint how dangerously hot it's ...

Recommended for you

US delays decision on Keystone pipeline project

Apr 18, 2014

The United States announced Friday a fresh delay on a final decision regarding a controversial Canada to US oil pipeline, saying more time was needed to carry out a review.

New research on Earth's carbon budget

Apr 18, 2014

( —Results from a research project involving scientists from the Desert Research Institute have generated new findings surrounding some of the unknowns of changes in climate and the degree to which ...

User comments : 3

Adjust slider to filter visible comments by rank

Display comments: newest first

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.
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?
You should educate yourself before posting.
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 .... !!.

More news stories

China says massive area of its soil polluted

A huge area of China's soil covering more than twice the size of Spain is estimated to be polluted, the government said Thursday, announcing findings of a survey previously kept secret.

UN weather agency warns of 'El Nino' this year

The UN weather agency Tuesday warned there was a good chance of an "El Nino" climate phenomenon in the Pacific Ocean this year, bringing droughts and heavy rainfall to the rest of the world.

NASA's space station Robonaut finally getting legs

Robonaut, the first out-of-this-world humanoid, is finally getting its space legs. For three years, Robonaut has had to manage from the waist up. This new pair of legs means the experimental robot—now stuck ...

Ex-Apple chief plans mobile phone for India

Former Apple chief executive John Sculley, whose marketing skills helped bring the personal computer to desktops worldwide, says he plans to launch a mobile phone in India to exploit its still largely untapped ...

Filipino tests negative for Middle East virus

A Filipino nurse who tested positive for the Middle East virus has been found free of infection in a subsequent examination after he returned home, Philippine health officials said Saturday.

Egypt archaeologists find ancient writer's tomb

Egypt's minister of antiquities says a team of Spanish archaeologists has discovered two tombs in the southern part of the country, one of them belonging to a writer and containing a trove of artifacts including reed pens ...