Improving the accuracy of climate model projections with emergent constraints

December 10, 2019

The increase in carbon dioxide concentration in the atmosphere has warmed the Earth since the beginning of the industrial era. Climate models try to project how much this warming trend will continue, but they differ in their global-mean temperature response to increasing concentrations of greenhouse gases. This is called climate sensitivity, according to Dr Florent Brient, a postdoctoral research scientist at the Centre National de Recherches Météorologiques (Météo-France/CNRS), France, and author of a recently published study that reviews a new method, known as emergent constraints, which attempts to use information about the current climate to constrain the evolution of climate in the future.

The study's findings were published on December 10th 2019 in Advances in Atmospheric Sciences.

In order to accurately predict how much the Earth will warm in the future, one needs to know how atmospheric carbon dioxide concentrations will evolve, together with an accurate assessment of climate sensitivity. Should carbon dioxide levels double, models predict the Earth would warm by 1.2 degrees Celsius, which induce changes that may either temper these effects or drive further warming. For example, an increase in warming increases atmospheric moisture, which provides a positive feedback that would drive further warming since water vapor is a potent greenhouse gas. Warming also melts sea-ice and snow which reflect sunlight away from the Earth -- known as the albedo effect. On the other hand, an increase in cloud cover, for example, could provide negative feedback, as the lowest clouds also reflect sunlight away from the Earth. However, since clouds are related to various dynamic scales and their radiative effects vary considerably in height, their effects on surface warming are complex. Consequently, clouds remain a major source of model disagreement.

In this paper, Dr Brient reviews the concept of emergent constraints and describes published emergent constraints, which reduce uncertainties in various simulated climate changes. The author discusses potential connections between emergent constraints and the influence of statistical methodologies in the quantification of these more likely projections. Finally, the author tries to verify whether emergent constraints can collectively reduce the spread in climate sensitivity provided by climate models.

"Emergent constraints are useful for narrowing the spread of climate projections and for guiding the development of more realistic climate models," said Brient. "However, they are sensitive to various factors, such as the way statistical inference has been performed or how observational uncertainties have been obtained. Therefore, more consistency across emergent constraints are needed for better cross-validation of more likely projections."

"The upcoming sixth phase of the Coupled Model Intercomparison Project (CMIP6) will most likely boost the enthusiasm of emergent constraints, by allowing a better understanding of certain climate phenomena and a further narrowing of their uncertain projections," said Brient. "However, this calls for sharing statistical methods used for these quantifications, as we have done in this paper," he adds.

According to Brient, two questions remain to be solved. Firstly, "what are the connections between the different predictors used for narrowing projections a given climate change? A better understanding of the links between circulation and clouds would help make progress in this regard," said Brient. And secondly, "how can the spread in climate projections be reliably narrowed if emergent constraints disagree with each other? This suggests that some emergent constraints are more trustworthy than others, but this remains to be investigated."
-end-


Institute of Atmospheric Physics, Chinese Academy of Sciences

Related Climate Models Articles from Brightsurf:

Polar ice, atmospheric water vapor biggest drivers of variation among climate models
A Florida State University researcher is part of a team that has found varying projections on global warming trends put forth by climate change scientists can be explained by differing models' predictions regarding ice loss and atmospheric water vapor.

Revising climate models with new aerosol field data
Advanced field measurements of how quickly aerosol particles are pulled out of the air can help improve climate predictions - and air quality forecasts.

Simpler models may be better for determining some climate risk
Typically, computer models of climate become more and more complex as researchers strive to capture more details of our Earth's system, but according to a team of Penn State researchers, to assess risks, less complex models, with their ability to better sample uncertainties, may be a better choice.

Atmospheric scientists study fires to resolve ice question in climate models
Black carbon from fires is an important short-term climate driver because it can affect the formation and composition of clouds.

New soil models may ease atmospheric CO2, climate change
To remove carbon dioxide from the Earth's atmosphere in an effort to slow climate change, scientists must get their hands dirty and peek underground.

Patterns in permafrost soils could help climate change models
A team of scientists spent the past four summers measuring permafrost soils across a 5,000 square-mile swath of Alaska's North Slope.

Latest climate models show more intense droughts to come
An analysis of new climate model projections by Australian researchers from the ARC Centre of Excellence for Climate Extremes shows southwestern Australia and parts of southern Australia will see longer and more intense droughts due to a lack of rainfall caused by climate change.

Some of the latest climate models provide unrealistically high projections of future warming
A new study from University of Michigan climate researchers concludes that some of the latest-generation climate models may be overly sensitive to carbon dioxide increases and therefore project future warming that is unrealistically high.

A Europe covered in grasslands or forests: innovation and research on climate models
An experiment to better understand how atmospheric variables respond to land use changes.

How tiny water droplets form can have a big impact on climate models
Droplets and bubbles are formed nearly everywhere, from boiling our morning coffee, to complex industrial processes and even volcanic eruptions.

Read More: Climate Models News and Climate Models Current Events
Brightsurf.com is a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for sites to earn advertising fees by advertising and linking to Amazon.com.