The ambitious plan to limit global warming to “well below” 2 degrees Celsius is abstract and invites misunderstanding, a team of Swiss researchers claims.
According to Sonia Seneviratne, professor of land-climate dynamics at Swiss Federal Institute of Technology (ETH Zurich), many people will interpret two degrees globally as two degrees of warming in their region and, accordingly, will not be proactive enough about reducing CO2 emissions in their countries.
The problem is that, according to various climate models, the temperature will rise more sharply over land than over oceans.
The big question, therefore, is how a maximum of two degrees global warming will affect individual regions of the world.
To understand this, a team of climate researchers from Switzerland, Australia and Britain led by Seneviratne has calculated the levels of extreme and average temperatures, as well as of heavy precipitation, that will occur in individual regions if the average global rise in temperature is taken as a reference.
Recently published in the journal Nature, the study based their calculations on several existing climate scenarios, as well as on the assumed and effective development in atmospheric CO2 concentration.
The scientists tested their new model using four examples: the Mediterranean, the USA, Brazil and the Arctic. For each of these regions, the researchers computed a separate graphical representation.
For the Mediterranean, the results reveal the following: if the global average temperature increases by 2 degrees Celsius, the region will see mean temperatures increase by 3.4 degrees Celsius on average.
“If, however, our aim is to limit warming in the Mediterranean to 2 degrees Celsius, then the global temperature must rise by no more than 1.4 degrees Celsius,” the authors noted.
The most extreme changes could be seen in the Arctic. With global warming of 2 degrees Celsius, the average temperatures in the far north increased by 6 degrees Celsius.
The 2 degrees Celsius target for the Arctic had already been exceeded when global warming reached 0.6 degrees Celsius on average.
The study illustrates that the 2 degrees Celsius target cannot be met in many regions of the world, even if it were adhered to on a global scale.
“We wouldn’t have expected the effects to be so clear-cut,” emphasised Dr Markus Donat, a researcher at the ARC Centre of Excellence for Climate System Science in Australia.
According to Seneviratne, anyone can use these calculations to see how 2 degrees Celsius of warming would affect their region.
This makes them a valuable tool for politicians and decisions-makers, as well as for civilians, agriculture and the tourism industry.