The window to avoid dangerous global warming is narrowing

Scientists at McGill University have determined that the threshold for dangerous global warming will likely be crossed between 2027 and 2042. This is a much narrower window than the previous IPCC estimate of between 2020 and 2052. 

Using a new method for projecting Earth’s temperature, the researchers have reduced some of the uncertainties surrounding future warming. 

The climate models that are used to project future temperatures play an important role in understanding the Earth’s climate. These models are used to incorporate different factors that interact to affect the climate, such as the atmosphere, ocean, ice, and the sun. While climate models are based on our clearest understanding of Earth and its natural processes, there are still many unknowns.

“Climate skeptics have argued that global warming projections are unreliable because they depend on faulty supercomputer models,” said study co-author Professor Bruno Tremblay. “While these criticisms are unwarranted, they underscore the need for independent and different approaches to predicting future warming.”

Temperature projections typically have such wide ranges that it is difficult to pinpoint the potential outcomes of different mitigation scenarios. For example, if atmospheric CO2 concentrations are doubled, the models used by the IPCC predict a global average temperature increase between 1.9 and 4.5 degrees Celsius. This estimate represents two extremes, with moderate climate changes on the lower end and catastrophic outcomes on the upper end.

“Our new approach to projecting the Earth’s temperature is based on historical climate data, rather than the theoretical relationships that are imperfectly captured by the GCMs. Our approach allows climate sensitivity and its uncertainty to be estimated from direct observations with few assumptions,” said study co-author Raphael Hebert.

In their study, the researchers introduced the new Scaling Climate Response Function (SCRF) model to project the Earth’s temperature from now through 2100. The model is based on historical data, and reduces prediction uncertainties by about half compared to the approach currently used by the IPCC. 

The researchers found that the threshold for dangerous warming, which exceeds 1.5 degrees Celsius above pre-industrial levels, will likely be crossed between 2027 and 2042. The experts also predict that average warming will be a little lower, by about 10 to 15 percent, compared to the IPCC estimate. However, the “very likely warming ranges” of the SCRF model were still within the range projected by the IPCC.

“Now that governments have finally decided to act on climate change, we must avoid situations where leaders can claim that even the weakest policies can avert dangerous consequences,” said Professor study co-author Shaun Lovejoy. “With our new climate model and its next generation improvements, there’s less wiggle room.”

The study is published in the journal Climate Dynamics. 

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By Chrissy Sexton, Earth.com Staff Writer