2 degrees is the goal, not a safe zone

Research results were published in the international academic journal Nature, showing that even if the global temperature rise is limited to 2 degrees compared to pre-industrial levels, it may not be enough to prevent 'extreme climate outcomes'.

The researchers used various global climate models to simulate extreme climate events that could occur under a 2-degree warming scenario. The subjects of analysis were three types of disasters: drought in granary areas, floods in densely populated areas, and fire weather in forest areas.

Why this is important

The study's most notable finding is that 'worst case scenario' projections of 2 degrees of warming are often more severe than 'average' scenarios of 3 or 4 degrees of warming. This suggests that policymakers may underestimate the true risk if they base their responses simply on average forecasts.

“From a risk management perspective, it is very important for policymakers to take these potential extreme situations into account,” said Professor Erich Fischer from ETH Zurich in Switzerland. He warned that changes occurring in certain regions could be "much higher" than the global average.

Limits of multi-model averaging

Scientists have typically used the 'multimodel mean' method, which averages and presents simulation results from multiple climate models. The Intergovernmental Panel on Climate Change (IPCC) has also used this method to produce a number of maps and forecasts.

Professor Fisher acknowledged that multi-model averaging was an "incredibly valuable" communication tool and a way to "simplify" complex results. However, in terms of risk management, he pointed out that focusing only on averages "can lead to misunderstandings."

The researchers selected 42 models from the CMIP6 project, the most widely used in the latest IPCC report, and conducted an analysis. The distribution of model results for each disaster type was evaluated, ranked by severity, and compared to the multi-model average of the 2-, 3-, and 4-degree rise scenarios.

Historical context of this study

In the 2015 Paris Agreement, the international community agreed to limit the rise in global temperature to within 2 degrees compared to pre-industrial levels and, if possible, to strive to keep it from exceeding 1.5 degrees. Since then, 2 degrees has become a key reference point for climate policy.

However, the global average temperature has already risen by about 1.1 to 1.2 degrees compared to pre-industrial times, and the prevailing forecast is that if the current trend of greenhouse gas emissions continues, it will exceed 2 degrees within this century. This study shows that the 2-degree target, which has been considered a 'safe limit', needs to be reexamined.

Future outlook [AI analysis]

A scientist who was not involved in the study said the results showed "a sobering reality" and "demonstrate that the risk of 2 degrees of global warming may be much higher than previously thought." He added that the research methodology would make a "very useful contribution" to future "global assessments of avoidable climate change risks."

The study is likely to require changes in the way climate policy is made. Instead of simply basing adaptation plans on average forecasts, a more comprehensive risk management approach that takes into account worst-case scenarios will be needed. In particular, it appears that more conservative preparedness measures will be required in specific areas such as food security, flood prevention, and forest fire response.