【気候科学】世界の平均気温上昇が2℃を大きく下回るようにするために必要なテコ入れ

National plans to address climate change after 2020 - submitted in preparation for the December 2015 Paris Agreement - imply a rise in global temperatures that would far exceed the limit dictated by the climate treaty. The authors of a Perspective published in this week’s Nature suggest that ambitious efforts are required to maintain a reasonable chance of keeping warming well below 2 °C relative to pre-industrial levels.

The Intended Nationally Determined Contributions (INDCs) describe how individual countries plan to mitigate their greenhouse gas emissions in order to meet the global target of preventing temperatures from rising by more than 2 °C and pursuing options that would further limit the increase to 1.5 °C.

Niklas Hohne and colleagues assess the emissions implications of the current INDCs and find that they imply a global warming of 2.6-3.1 °C by 2100 - an improvement from current- and no-policy scenarios, but still well above the 2 °C target. The authors further show that even with accelerated action after 2030, the ability of the current INDCs to meet the 2 °C goal is severely limited. However, as the Paris Agreement requires countries to submit new, increasingly ambitious INDCs every five years, the authors conclude that keeping global warming well below 2 °C remains possible with greater emissions reductions in the coming decade and with the continuing momentum of action by national and non-state actors, including businesses and citizens.