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Alpine diluvium of Châteauneuf-du-Pape
On August 9, the Intergovernmental Panel on Climate Change (IPCC) published the first part of its sixth report on scientific knowledge of climate systems and climate change. Meanwhile, the French national meteorological service has indicated that temperatures in France could exceed 50°C in some places in 2030. Faced with this situation, limiting warming to 1.5°C, as recommended by the IPCC, requires in-depth changes. In this interview, we hear from Marie-Noëlle Woillez, who has a PhD in climate modeling and is head of research programs on climate-change impact at Agence Française de Développement (AFD).
We are witnessing an intensification of successive record-breaking high temperatures. Last June, in British Columbia, Canada, the temperature hit a new record of 49.5°C. What can we expect in the short and medium term?

Marie-Noëlle WoillezMarie-Noëlle Woillez: Global warming is accompanied by an increase in the frequency and intensity of heatwaves practically all over the world. This phenomenon has been clearly observed over the last few decades and was also predicted long ago by climate models.

You may recall the record high of 45.9 °C reached in Southern France in June 2019. Such summer heatwave temperatures that are today considered exceptional could become the norm in the coming decades, depending on the extent of future warming, which is affected by greenhouse gas emissions.

We should keep in mind that tropical regions are especially at risk. And even if the people living there are more used than we are to high temperatures, there are physiological limits to the temperature that a human being can bear. So, regions such as Southeast Asia could face heat conditions that are dangerous to health several months a year, and this as early as the middle of the century.

Read also: the first part of the sixth IPCC report, published on August 9, 2021

How achievable is the goal of limiting temperature increase to +1.5°C?

M-N. W.: The global average temperature increase over the 2011-2020 period is estimated to be about 1.09°C compared to the end of the 19th century, and the last five years (2016-2020) have been the warmest five-year period on record since at least 1850.

At the current rate of warming, we could surpass the 1.5°C threshold before 2050, perhaps as early as the 2030s. Staying below 1.5°C would require reducing greenhouse gas emissions by 40-50% by 2030, achieving carbon neutrality by 2050, and removing CO2 from the atmosphere in the second half of the century.

However, emissions continue to increase—if we don’t count the decrease linked to the Covid-19 pandemic, which is probably temporary. In other words, while limiting temperature increase to 1.5°C is still theoretically possible, the socio-economic change required for it is such that it’s highly doubtful we can effectively implement it fast enough.

That said, as many scientists have pointed out, every half degree counts. Even if the 1.5°C target seems unrealistic, that doesn’t mean it’s "too late" and that it’s useless to try to drastically reduce our emissions. Indeed, warming of 2°C will always be less harmful than warming of 2.5°C or more! 

What levers should be used to achieve the objective?

M-N. W.: In 2018, the IPCC published a special report on the impacts of global warming of 1.5°C. It emphasized the need for swift large-scale changes in all fields and sectors, such as energy, land use, development, urban planning, infrastructure, and industry. It also pointed out the considerable difficulties faced in order to implement those changes.

Compared to past changes in specific sectors, the pace of transition required is not necessarily unprecedented. However, there is no historical analogy in terms of the magnitude of the socio-economic transformation needed. The difficulties are also related to political, economic, and institutional contexts, and sometimes to the trade-offs to be found in achieving certain sustainable development goals.

It’s not possible for a single, universal solution to meet the goals. Limiting emissions requires a wide range of mitigation measures, the choice of which will depend on how energy and resource demand will evolve, how fast we decarbonize our activities, and the hypothetical use of carbon capture and sequestration.

This last hypothesis is moreover very controversial because its feasibility on the scale needed hasn’t been proven. In any event, massive decarbonization of the energy sector will be essential, but demand management—that’s to say reduction in overall energy consumption—is undoubtedly a lever not to be neglected if we want to avoid relying on technologies yet to be invented.

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