Summary

Investing to limit global warming to 1.5 °C between now and 2050 would cost four to five times less than repairing the harm that a 2 °C temperature increase would cause to people, ecosystems and infrastructures. This statistic comes from an international study to which IRD and CNRS researchers have participated, published on 20 September 2019 in the journal Science. The authors warn decision-makers about the urgent need to accelerate their efforts to limit greenhouse gas emissions.

Bloc de texte

The scientific community regularly documents the impacts of climate change on the environment, biodiversity and the well-being of populations around the world. In May 2019, the Intergovernmental Platform on Biodiversity and Ecosystem Services (IPBES) announced that around 1 million animal and plant species are now threatened with extinction, particularly in the next few decades. Climate change is a contributor to this unprecedented destruction, even if it is not the only factor.  

In this study, an international team (from Australia, Germany, France, Jamaica, Italy, England, Argentina, Japan, Indonesia, South Africa, the United States, China and the Bahamas) analysed the database of the IPCC Special Report on Global Warming of 1.5 °C, published in October 2018. The researchers compared the damage that would be caused by global warming of 1.5 °C by 2050 (relative to the pre-industrial era) to the damage associated with a 2 °C increase in temperatures. They also evaluated the total investment required from States (again between now and 2050) to limit global warming to 1.5 °C, and that required to repair the harm caused in the +2 °C scenario.

A “win-win” strategy

The results of this study, published in Science, confirm the considerable advantages of limiting the increase to 1.5 °C above global pre-industrial temperatures. The benefits would be especially significant for forests, biodiversity, food security, health, Arctic ecosystems and coral reefs.


According to the researchers, reducing the extent of climate change is also a good investment. “Over the next few decades, the cost of taking action to limit global warming would probably be just a quarter of the cost associated with the damage climate change could cause to people, ecosystems and infrastructures. That represents at least a 4-for-1 return on investment,” states Ove Hoegh-Guldberg, a professor at the University of Queensland (Australia) and the lead author of the study.

Appeal to reduce greenhouse gas emissions

“The Mediterranean region, like many arid zones, is particularly vulnerable to the increasing numbers of droughts and heat-waves,” explains Joël Guiot, CNRS research director and co-author of the study.

“Their effects are amplified by human activities, such as agriculture, overexploitation of the sea, rapid urbanization, industry and tourism. This is a real vicious circle for populations.”

The authors of the study are therefore appealing to decision-makers to accelerate their efforts to limit global warming, emphasising the inadequacy of the current commitments to reduce greenhouse gas emissions.

“West African countries are already experiencing increasingly intense climate extremes, which can threaten food security and increase flood risks in the main towns of the central Sahel,” warns Arona Diedhiou, IRD climatologist and atmospheric physicist, and co-author of the study. “Coastal erosion due to rising sea levels is a huge challenge for the main towns and cities along the region’s coast. We need a profound shift, at both the local and global levels, towards low carbon emission development trajectories. This will benefit the countries’ economies and protect the well-being of African populations.”


Contacts: arona.diedhiou@ird.fr ; guiot@cerege.fr 

Reference : Hoegh-Guldberg, O., D. Jacob, M. Taylor, T. Guillén Bolaños, M. Bindi, S. Brown, I. A. Camilloni, A. Diedhiou, R. Djalante, K. Ebi, F. Engelbrecht, J. Guiot, Y. Hijioka, S. Mehrotra, C. W. Hope, A. J. Payne, H-O Pörtner, S. I. Seneviratne, A. Thomas, R. Warren, G. Zhou. The human imperative of stabilizing global climate change at 1.5°C, Science, 19 septembre 2019.