The simulations of climate change that best capture current planetary conditions are also those that predict the most severe levels of human-driven warming, according to a statistical study published in the journal Nature on Wednesday .
The study, conducted by Patrick Brown and Ken Caldeira of the Carnegie Institution for Science in Stanford, California, examined the high-power simulations of climate change, or "models," which researchers use to project the future of the planet over the physical equations that govern the behavior of the atmosphere and the oceans.
Next, the researchers analyzed the models that best captured the current high atmospheric conditions predicted. These models generally predicted a higher level of warming than the models that did not capture these conditions either.
The study adds to a growing body of bad news about how human activity is changing the planet's climate and how terrible those changes will be. But according to several external scientists consulted by The Washington Post, although the investigation is well executed and intriguing, it is not definitive either.
"The study is interesting and disturbing, but the details need more research," said Ben Sanderson. , a climate expert at the National Center for Atmospheric Research in Boulder, Colorado.
Brown and Caldeira are far from being the first to study such models in a large group, but they did it with a twist.
In the past, it has been common to combine the results of dozens of these models, and thus give a range of how much the planet could heat for a given level of carbon dioxide emitted into the atmosphere. That is the practice of the main international climate science body, the United Nations Intergovernmental Panel on Climate Change.
In contrast, Brown and Caldeira compared the performance of these models with recent satellite observations of the real atmosphere and, in particular, the balance of incoming and outgoing radiation that ultimately determines the temperature of the Earth. Then, they tried to determine which models worked best.
"We know enough about the climate system that it does not make sense to necessarily toss all the models into a pool and say, we're blinded to what models might be good and what could be bad," said Brown, a postdoc at the Carnegie Institution.
The research found that the models that do the best job in capturing the current "energy imbalance" of the Earth, as expressed by the authors, are also those that simulate more warming in the future of the planet.
Under a scenario of high warming in which large emissions continue throughout the century, the models as a whole give an average warming of 4.3 degrees Celsius (or 7.74 degrees Fahrenheit), plus or minus 0.7 degrees Celsius, for the period between 2081 and 2100, the study said. But the best models, according to this test, gave a response of 4.8 degrees Celsius (8.64 degrees Fahrenheit), plus or minus 0.4 degrees Celsius.
In general, the change is equivalent to increasing the projected warming by 15 percent. The researchers presented this figure to capture the findings:
When it comes to the question of why the finding came about, it seems that much of the result had to do with how the different models handled one of the biggest uncertainties about how Planet will respond to climate change.
"This is really about the clouds," said Michael Winton, a leader in the climate model development team at the Geophysical Fluid Dynamics Laboratory of the National Oceanic and Atmospheric Administration, who discussed the study with The Post, but he was not involved in the investigation.
Clouds play a crucial role in climate because, among other roles, their light surfaces reflect incoming solar radiation into space. So, if the clouds change under global warming, that in turn will change the global climate response.
However, the way in which clouds could change is quite complex and models can not fully capture this behavior due to the small scale in which it occurs, programs instead tend to include assumptions based on statistics on behavior From the clouds. This is called " parameterization".
But the researchers are not quite sure that the parameterizations are correct. "So, what you're seeing is that the behavior of what I would say is the weak link in the model," Winton said.
This is where the Brown and Caldeira study comes in, basically identifying models that, by virtue of this programming or other factors, seem to do a better job of representing the current behavior of the clouds. However, Winton and two other scientists consulted by The Post said they respected the intent of the study, but were not completely convinced.
Sanderson of the National Center for Atmospheric Research, was concerned that the current study might find an effect that was not really there, in part because the models are not completely independent from each other, they tend to overlap in many areas.
"This approach is designed to find relationships between future temperatures and the things we can observe today," he said. . "The problem is that we do not have enough models to be sure that the relationships are solid, the fact that the models of different institutions share components makes this problem worse, and the authors have not addressed this at all."
"It's great that people are doing well and we should continue to do this kind of work, it's an important complement to the sensitivity assessments of other methods," added Gavin Schmidt, who directs the Goddard Institute of Space Studies of the POT. "But we should always remember that it is the consistency of the evidence in such a complex area that it usually gives robust predictions."
Schmidt noted that future models could make this current finding disappear, and also noted the increase in warming in the best models found in the study was relatively small.
The principal author of the Brown study argued, however, that the results have a significant implication in the real world: they could mean that the world can emit even less carbon dioxide than we think if it wants to keep warming the target widely Accepted of 2 degrees Celsius (3.6 degrees Fahrenheit). This would mean reducing the "carbon budget".
The study "would imply that to stabilize the temperature at 2 degrees Celsius, it would have to have 15 percent less accumulated CO2 emissions," he said.
The world I can afford, as it is, it is very difficult to see how even the current carbon budget can be met. In general, it is considered that the world is misguided when it comes to reducing its emissions, and with continued economic growth, the challenge is enormous.
In this sense, that the new research will have to gain acceptance may be at least temporary indulgence for those responsible for formulating policies, which in fact would be in a difficult position if it were shown to be definitely correct.