The threshold for dangerous global warming will probably cross between 2027 and 2042. This is a much narrower window than the Intergovernmental Panel on Climate Change's estimate of between now and 2052.
Researchers introduce a new and more precise way to project the Earth's temperature. Based on historical data, it considerably reduces uncertainties compared to previous approaches.
Scientists have been making projections of future global warming using climate models for decades. These models play an important role in understanding the Earth's climate and how it will likely change.
Climate models are mathematical simulations of different factors that interact to affect Earth's climate, such as the atmosphere, ocean, ice, land surface and the sun. While they are based on the best understanding of the Earth's systems available, when it comes to forecasting the future, uncertainties remain.
Climate sceptics have argued that global warming projections are unreliable because they depend on faulty supercomputer models. While these criticisms are unwarranted, they underscore the need for independent and different approaches to predicting future warming.
Wide ranges in overall temperature projections have made it difficult until now to pinpoint outcomes in different mitigation scenarios. For example, if atmospheric CO2 concentrations are doubled, the General Circulation Models (GCMs) used by the Intergovernmental Panel on Climate Change (IPCC), predict a very likely global average temperature increase between 1.9 and 4.5C. This is a vast range covering moderate climate changes on the lower end and catastrophic ones on the other.
The 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. It allows climate sensitivity and its uncertainty to be estimated from direct observations with few assumptions.
Source: McGill University