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The 2022 Earth Day and the latest IPCC report on mitigation: the main evidences in the article by Roberto Buizza, as a professor at Sant'Anna School. “The evidence is clear: the time for action is now”

Publication date: 15.04.2022
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On the occasion of the International Earth Day, which is celebrated on April 22 of each year, at the initiative of the United Nations, to remember the importance of protecting the planet and defending the environment, Roberto Buizza, as a Full Professor of the Sant'Anna School, writes an article to present the main evidence emerging from the new report of IPCC - Intergovernmental Panel on Climate Change: “The evidence is clear: the time for action is now”

di Roberto Buizza

“I suggest starting the 2022 Earth Day (the 22nd of April) reminding ourselves the key messages of the latest report of the ‘Intergovernmental Panel on Climate Change’ (IPCC) (link:”.

“The report says that global warming can be controlled, and the impacts of climate change limited, if greenhouse gases (GHGs) emissions are reduced immediately in a substantial way. We have the technologies to achieve this, technologies that in the last two decades have become cheaper and economically more sound than technologies based on fossil fuels. The economic benefits linked to a reduction of the GHG emissions outweigh the costs of de-carbonisation”.

“The report reminds us that in the last decade, from 2010 to 2019, the GHG emissions have continued to grow, but also states that a reduction of 43% of the emissions by 2030 (compared to the 2019 level) and of 84% by 2050, could limit global average warming to below 1.5 oC degrees. A slower reduction of 27% by 2030 (again with respect to the 2019 level) and of 67% by 2050 could limit the warming between 1.5 and 2 oC degrees”.

“These are a few of the conclusions of the ‘Summary for Policy Makers’ of the latest IPCC report, written by the IPCC Working Group III and published on the 4th of April 2022 (SPM-WGIII; link:”.

“SPM-WGIII is the latest of the 6th series of the IPCC Assessment Reports (AR6), which are providing the world with an updated view of the state of the climate and of the impacts of the ongoing global warming, and an overview of the latest scientific and technological advances that can help us addressing climate change. SPM-WGIII follows the report of Working Group I on ‘The science of Climate Change’, published in august 2021,, and the report of Working Group II on ‘Impacts, adaptation and vulnerability’, published in February 2022, (link:”.


What is the state of the climate?

“In March 2022, the atmospheric carbon dioxide (CO2) concentration has reached 418 ppm (parts per million), as can be seen, e.g., from the observed time-evolution of the GHG concentrations at the Mauna Loa Observatory:”.

“Reconstructions of the CO2 concentration of the distant past, based on the analysis of sediments or ice cores, indicate that we need to go back 2.5 million years to detect CO2 levels above 400 ppm. They also indicate that in the last 800,000 years and up to 1900 the CO2 concentration oscillated between about 180 and 300 ppm, before starting to climb after 1900 to the current levels. Observations show that not only CO2, but also the other main GHGs continue to rise: methane (CH4) has passed 1,900 ppb (parts per billion) and nitrous oxide (N2O) has passed 335 ppb”. 

“The most evident impact of the continuous rise of the GHG emissions linked to human activities is global warming: the globally-averaged surface temperature now stands about 1.2 oC above the pre-industrial value (defined as the mean temperature between 1850 and 1900). But some parts of the globe, e.g., the Polar caps and the Mediterranean region, experience average warming levels much higher than 1.2 oC. For example, over Europe and Italy the average warming stands at about 2.5 oC with respect to the pre-industrial level. This means that a further future warming of about 1 oC degree could translate, for these ‘climate hot spot regions’, into a further warming of at least 2 oC degrees”.

“Climate warming has been causing a sea-level rise and the melting of glaciers and ice caps. Since 2006, an acceleration of almost a factor of 3 of the sea-level rise has been detected, with the average sea-level increasing by about 3.6mm/y, compared to about 1.4mm/y before 2006. This acceleration is partly due to the warming of the oceans and partly due to the melting of glaciers. If we consider the polar caps, observations have been showing that both their extension and thickness have been decreasing: the first months of 2022 have seen the extension of both polar caps below the historical minima detected so far (see, e.g., the observed extension report by the National Snow and Ice Data Center americano, NSIDC: link”.


What does the latest IPCC report say on mitigation?

“SPM-WGIII reports that GHG emissions continue to grow, but with a smaller growth rate than 10 years ago: observations show that between 2010-2019 global emissions have increased, on average, by 1.3%, while the decade before (2000-2009) they increased by 2.1%. It also reminds us that most of the GHGs have been emitted in the last decades: for example, 17% of all GHG injected in the atmosphere between 1850 and today, were injected in the atmosphere in the last decade, between 2010-2019. This fact is another reason why we have to reduce emissions immediately and drastically if we want to limit global warming and the impacts of climate change”.

“SPM-WGIII talks explicitly of the geographical disparity of the GHG emissions. If we consider, for example, the emissions of CO2 injected into the atmosphere between 1850 and 2019, the regions that contributed most to the current levels are North America (which emitted 23% of the total amount) and Europe (with 16%), followed by East Asia (12%), Latin America and the Caribbeans (11%), and then to the other regions of the world. The last 30 years have seen large variations in the relative contribution of the different regions, as a consequence of the economic growth, and of the transformation of the economies of many countries that has seen a shift of manufacturing towards the East, and the concentration of some of the western economies into less-energy-intensive sectors (e.g., financial services). Between 1990 and 2020, the relative contribution to the global emissions of North America has decreased from 18% to 12%, and the European contribution has decreased from 16% to 8%. By contrast, in the same period the relative contribution of East Asia has increased from 13% to 27%”.

“If we consider the GHG emissions per capita, between 1990 and 2019 the global annual-mean value has increased from 7 to 7.8 tCO2-eq (tons of CO2-equivalent emissions), with geographical variations of up to a factor of 10, with some countries characterized by emissions per capita of 2.0 tCO2-eq, and others by values around and above 20 tCO2-eq. If we consider Italy, in 2019 average emissions per capita were 7.2 tCO2-eq, a value which is close to the average of the 27 countries of the European Union, 8.4 tCO2-eq (data from Eurostat:”.


“With respect to mitigation, SPM-WGIII points out that between 2000 and today the unit cost of renewable energy production has decreased substantially, and today these sources of energy are economically convenient compared to sources linked to fossil fuels (Fig. 1). This economical advantage of the renewable sources should further promote their adoption, which has also been increasing dramatically during the past 20 years”.

Is there a chance to keep global warming below 1.5 or 2 oC degrees?

“The analysis of more than 1,200 projections of the future climate, generated by different groups of scientists using state-of-the-art Earth-system models, indicates that global warming can be limited to 1.5 or 2 oC degrees if we reduce drastically and immediately GHG emissions”.

“Results indicate that a reduction of the global emissions of 43% by 2030 (with respect to the 2019 values), and of 84% by 2050, would limit global warming below 1.5 oC degrees (with respect to the pre-industrial level).  A less drastic reduction of 27% by 2030 and 67% by 2050 (respect to the 2019 values) would limit global warming to between 1.5 and 2.0 oC degrees. Anything less than these amounts, or even worse a continued increase in the emissions, would bring us to warming levels between 2 and 5 oC degrees”.


Can Italy aim to reduce its emissions by these amounts? 

“To reduce its emissions by 43% by 2030, between 2020 and 2030 each country has to reduce its annual emissions by about 5%, while to reduce its emissions by 27% it has to reduce its annual emissions by about 2.8%”.

“Figure 2 shows that In 2018 the Italian emissions were 85% of the 1990 ones, and that between 1990 and 2018 Italy reduced its annual emissions, on average, by 0.5%. If we consider only the last 10 years, annual emissions were reduced, on average, by 2.3%, thus indicating an acceleration of the de-carbonisation. Figures 2 Also shows the values of the UK: in 2018 its emissions were 69% of the 1990 ones, between 1990 and 2018 reduced its annual emissions, on average, by 1.3%, and during the last 10 years it decreased its emissions, on average, by 1.8%”.

“If we compare these values with the 5% annual reduction level required to keep global warming below 1.5 oC, we see that both these countries have to accelerate de-carbonisation by a factor of between 2 (Italy) and 3 (UK). An acceleration of the de-carbonisation would be required also to keep global warming below 2 oC, to bring the average reduction of the GHG emissions from 2.3% (Italy) or 1.8% (UK) to 2.8%”.

“SPM-WGIII says that these reduction levels are possible if we proceed with a substantial reduction of fossil fuels, we transform the way we produce electricity to zero-net-emission power plants, we use green hydrogen as a way to accumulate energy, we make all production processes more efficient and we reduce consumption, and we re-design the way we match energy offer and demand. SPM-WGIII says explicitly that to keep global warming below 1.5 or 2 oC degrees, we will have to also use carbon capture and storage (CCS) systems, to compensate for the residual emissions of hard-to-abate sectors”.

What are the costs and benefits of reducing the GHG emissions?

“SPM-WGIII states that the benefits of keeping global warming below 2 oC outweigh the costs linked to the reduction of the GHG emissions. It talks about the co-benefits that can be derived from a reduction of the GHG emissions, expressed in terms of the Sustainable Development Goals (SDGs; link: It proposes that the SGDs are used to measure the impact of mitigation and adaptation policies. It talks about the need to maintain a strong link between mitigation and adaptation policies aimed to address climate change, and the need to achieve a more sustainable future and more social justice”.

“On this latter point, the report states that a further decrease of social justice, and the fact that some countries do not have enough economic and social resources could increase their vulnerability, and make them even less capable to adapt to climate change and to reduce emissions. Social justice must be translated into rich countries making resources available to the less developed countries, the ones that very likely have contributed less than others to the increase of the GHG in the atmosphere and are more exposed to the impact of climate change. Making resources and technologies available can help them develop economically, and address climate change”.


“The evidence is clear: the time for action is now” (da IPCC WGIII SPM).