In a letter published in Environmental Research Letters, an international group of researchers assesses how achieving the objectives of the Paris Agreement can limit the exposure of the population to droughts and heat waves
The Paris Agreement, adopted in 2015, aims to keep the global average temperature increase well below 2 °C compared to pre-industrial levels and to limit it to 1.5 °C in order to mitigate climate change and its effects. These effects occur also on hydro-meteorological extremes: heavy rainfall and floods, droughts and heat waves are among the phenomena affected by global warming. What could be the result of achieving the Paris Agreement’s goals on the exposure of population to these phenomena? Or, as a letter recently published in Environmental Research Letters titled: “Will the Paris Agreement protect us from hydro-meteorological extremes?
In order to answer, the authors, an international group of researchers from Joint Research Centre, University College London, Euro-Mediterranean Centre on Climate Change, Piksel srl and CIMA Research Foundation, have carried out a first combined assessment of the exposure of the population to some hydro-meteorological extremes.
A multi-risk analysis
Several studies have already shown how increase in average temperature of the planet can deeply influence some natural phenomena, producing different effects also depending on the geographical areas considered. However, usually the phenomena are evaluated individually; having an analysis that takes them into account together can be important to understand the overall risk involved and, therefore, improve long-term projections of their evolution.
“In our work we have focused on three specific phenomena: floods, droughts and heat waves”, explains Lorenzo Alfieri, researcher in Hydrology and Hydraulics Department at CIMA Research Foundation and co-author of the study. “In particular, we have tried to evaluate their possible evolution assuming three different scenarios of global average temperature increase; 3, 2 and 1,5 °C; these last two values represent the objectives of the Paris Agreement.”
The evaluation was conducted primarily by analyzing, on the basis of specific indicators, the different aspects of the combination of floods, droughts and heat waves, taking into account their intensity, duration, frequency and geographical distribution. Results were then combined, with the projections of one of the forecast scenarios used by the Intergovernmental Panel on Climate Change (IPCC), the intergovernmental body that studies climate change.
How population exposure changes
“The results obtained by analyzing the evolution of these three hydro-meteorological extremes suggest that containing the temperature increase within 2 °C would decrease the flood (?) exposure of the population by more than 50% in Africa, Asia and America, and about 40% in Europe, compared to what would happen with a temperature increase of 3 °C,” continues the researcher. “The decrease in exposure would be even greater if the global average temperature increase were contained within 1.5 °C: specifically, it would be 10% more for Africa, Asia and America, and up to 30% more for Europe”.
The authors themselves highlight some limitations of their analysis. For example, it was not possible to analyze the effects of events occurring simultaneously; nor was it possible to take into account the vulnerability of populations, a fundamental parameter for risk assessment. However, the results give a first important signal: “The data that emerge from our study already represent a strong indication of the benefits that would be achieved by meeting the objectives of the Paris Agreement, with a significant reduction in populations exposed to risk from the hydro-meteorological extremes analyzed,” Alfieri comments.
The results of the study, the authors write, are all more important if we consider that 2020 is also the year in which the parties will have to review their nationally determined contributions (NDCs), i.e. the objectives that individual nations have set themselves to achieve the objectives of the Paris Agreement and for which, according to estimates, their aggregate effect to date would lead to a temperature increase of 2.6-3.1 °C by the end of the century.