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Climate change: the latest IPCC report explained by its authors

On August 9, the first part of the sixth report of the IPCC (Intergovernmental Panel on Climate Change) was published that deals with the physical bases of climate change. The other two parts, one dedicated to impacts and vulnerability and the other to mitigation, will be published in early 2022.

The IPCC reports are designed to provide an up-to-date synthesis of all the scientific information on climate change available to date (14,000 publications have been reviewed in this report), so that it can be used by governments and institutions throughout the world. world as a basis for taking management action. In this case, one of the main conclusions of this first part dedicated to analyzing and projecting changes in the Earth’s climate system is clear: recent changes in the climate are widespread, rapid and increasingly intense, and are unprecedented in the thousands. of years.

“There is no longer any margin of doubt: the observed warming is caused by greenhouse gas emissions from human activities,” explained Yolanda Luna, head of the Training Center of the State Meteorological Agency (AEMET), in a seminar organized by the CSIC in which four Spanish authors of the IPCC report participated. In addition, and since the global average temperature has already risen 1.1 ° C from pre-industrial levels, limiting warming to 1.5 ° C requires very rapid and large-scale reductions in emissions.

In the case of not putting any limit on these emissions, the predictions indicate that by the end of the century we could exceed 5 ° C. What will happen if emissions are kept low or very low? The expert recalls that, even in these low emission scenarios, the climate system already has a certain inertia and it is likely that in the short term the planet will continue to warm, so it is expected that in the coming decades the global average temperature will continue in ascent. However, in the medium term we could contain the increase below 1.5-2 ° C, so the climate we will experience in the future depends on our present decisions.

Something similar happens in the oceans: “there the changes will last for years, they are very large masses that already have their own inertia”, explained Sergio Henrique Faria, professor at the Basque Center for Climate Change (BC3) and one of the authors of the report of the IPCC. “For example, in the case of ocean acidification, the drop in pH will continue to occur in the short term in all scenarios. Of course, this process could be stopped in the medium term if we manage to keep emissions at a low or very low level. And the same thing happens with sea level: the ice melts and there is no going back, so we have to think about how we are going to adapt to these impacts ”, adds the researcher, who also recalls that some changes could slow down and others could be stopped by limiting heating.

Climatic extremes

One of the chapters of the IPCC report refers to extreme events that are predicted to be increasingly frequent and severe. “This is a very relevant point: average changes are important and have consequences, but the main impacts of climate change on human societies are fundamentally related to extraordinary events, ” explained Sergio Vicente Serrano, researcher at the Pyrenean Institute of Ecology (IPE-CSIC) and one of the authors of this chapter. In preparing this section, six types of events have been taken into account: temperature extremes, extreme rainfall, floods, droughts, storms and compound events (simultaneous coexistence of different extremes).

The researcher clarifies that in this section forest fires have not been analyzed since “in many fires other factors that are not purely meteorological come into play: forest management, land use, existing means of dealing with fire, etc. Of course, heat waves and droughts cause fires to intensify or become more frequent but this has been analyzed in more detail in other chapters dedicated to the impacts of climate change ”.

Climate change in a regional key

Another novelty of this sixth IPCC report is that it analyzes in depth what is happening at the regional level, including an interactive atlas to visualize the evolution of the climate crisis and future impacts and that has been prepared by a team of researchers linked to the CSIC.

“45 new land regions have been considered, both oceanic and continental,” explains Francisco Doblas Reyes, researcher at the Barcelona Supercomputing Center (BSC-CNS). “In addition, not only have traditional climatic regions such as the Mediterranean been considered, but the knowledge associated with cities has been incorporated, which act as hot spots for climate change.”

“The atlas has been conceived to be more than a collection of maps, as it aims to offer a practical synthesis of all the information available for each region,” explains José Manuel Gutiérrez, director of the Institute of Physics of Cantabria (IFCA, CSIC-Univ Cantabria) and coordinator of the atlas. The researcher explains that this tool has two components: an application that offers all the regional climate data and models for a series of atmospheric indices and variables, and a second component that will be presented at the end of September and that shows synthesis information, easy to use. understand at the user level and facilitate decision-making for each region.

Regional differences are a very important aspect to understand the impact of climate change. For example, if the global average temperature is increasing and the sea level is also rising, a question that may arise is that all this should lead to an increase in precipitation. “This is indeed the case: average precipitation has increased globally, but there are very notable regional differences ,” says Sergio Vicente Serrano. “For example, evaporation has increased in oceanic or continental areas with high humidity, but not in arid areas. But, although evaporation increases at a global level, regional processes are very complex and this translates into very notable differences that not only depend on temperatures, but also on feed backs between surface and atmosphere, on uneven warming of oceanic and continental areas. , etc.”.

 

You can see the full seminar here:

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