"Climate change calls for urgent mitigation action": article by Roberto Buizza, full professor at the Sant'Anna School, about four key aspects to understand the need to reduce greenhouse gas emissions as soon as possible
"Understanding the inertia of the Earth-system components is key to explain why the state of the climate today is due to the accumulation of the emissions since the pre-industrial level, and why we need to act now to limit the future warming"
The Sant'Anna Magazine hosts a article by Roberto Buizza, full professor of Physics of the Earth System, Planets, Space and Climate, Interdisciplinary Research Centre for Sustainability and Climate at the Sant'Anna School, which analyses four fundamental aspects to understand the need to reduce greenhouse gas emissions as soon as possible.
by Roberto Buizza (*)
"The Copernicus Climate Change Service (C3S) of the European Union has just reported that the global-average temperature for the past 12 months (September 2023 – August 2024) is the highest on record for any 12-month period, at 1.64°C above the 1850–1900 pre-industrial average. It also reported that both the global-average and the European-average temperatures for boreal summer 2024 (June–August) were the highest on record.
Four aspects that are important to understand the need to act now: understanding the inertia of the Earth-system components is key to explain why the state of the climate today is due to the accumulation of the emissions since the pre-industrial level, and why we need to act now to limit the future warming. Knowing who is most responsible for the accumulated emissions is key to understand the current impasse in climate mitigation. Knowing what a tipping point is and how it could be surpass is essential to understand why we cannot delay emission reductions. Finally, knowing how Italian emissions have been evolving in the past decades illustrates how Italy has been acting to address climate change.
The inertia of the Earth system components increases the complexity of addressing climate change and explains the time lag between actions and responses. It explains why today’s actions will have impacts mainly in the distant future, and why present immediate actions are needed to avoid future damages and potential irreversible changes. Precisely because of this inertia, actions must be taken now to guarantee a viable future to the next generations.
There are no doubts that we, humans, are responsible for the ongoing climate change, uniquely characterized by a global warming happening over a very short time interval (about 1.5oC over about 100 years) compared to past natural climate variations. More precisely the continued use of fossil fuels (coal, combustion oil and gas) and the exploitation of land are the principal causes of the ongoing climate change. Some of us are more responsible than others. Given that a molecule of carbon dioxide (CO2) remains on the atmosphere for hundreds of years, the warming that we experience today is the result of the accumulation of the greenhouse gas emissions since the pre-industrial time, when the use of fossil fuels started growing substantially. If we compare the accumulated emissions between 1850 and 2019, we see that North America and Europe are the main responsible, as they contributed respectively to 23% and 16% of the 1850-2019 accumulated emissions, followed by Eastern Asia (12%), Latin America and the Caribbean (11%) and then the other regions.
A great disparity continues to exist between the emissions per capita of different regions, with, for example in 2019, North America characterized by about 18 tCO2-eq per capita, Europe 8 tCO2-eq per capita, and about 3 billion people with less than about 3.5 tCO2-eq per capita (data from the Intergovernmental Panel on Climate Change (IPCC) 6th Assessment Reports published in 2021-2022). It is also worth noting that the countries that have the least emissions per capita are often the ones hardest hit by the impacts of climate change, e.g. as measured by the Climate Risk Index (CRI) between 2000-2019, which depends on fatalities and economic losses, between 2000-2019.
2023 was the warmest year on record, and in the past 12 months (September 2023-August 2024) the global average temperature has been 1.64oC above the pre-industrial (1850-1900) level. In the past 20 years, global warming has been accelerating, from about +0.11oC every decade in 1980-2001, to about +0.25oC every decade in 2002-2023. As global emissions keep increasing, predictions under business-as-usual scenarios indicate that annual-mean global warming will very likely reach 2.0 oC sometime between 2037 and 2050. The continued warming could bring us over Earth-system tipping points, i.e. trigger quasi irreversible changes in some of the Earth-system components that drive the climate, such as the polar ice sheets, the Greenland glaciers or the Amazon forest. For example, in the Arctic as the cold season gets warmer and shorter, we could see an accelerated reduction of ice formation, and this could accelerate the melting in the warm months. The effect would be a substantial reduction in the sea-ice extent both in the warm and cold months, that could lead to ‘blue Arctic’ conditions, with substantial positive feedback on the Earth albedo, the decrease of which will potentially further accelerate global warming.
Italy in 2022 had about 0.7% of the world population, and in 1850-2022 emitted about 1% of the GHG accumulated emissions. In the past decades, Italy’s per capita emissions has been in line with European per-capita emissions: for example, in 2022 Italian emissions per capita were 6.5 t CO2-eq, and the European ones 7.5 t CO2-eq. If we consider the last decade 2013-2022 for which data are available, Italy reduced emissions on average by 0.5% per year, making it almost impossible to achieve the European Union 'fit-for-55' target (a reduction of the emissions by 55% compared to the emissions in 1990) in 2030. Italy could still reach this target, if in the years 2023-2030 it reduces them on average by 7% per year. Note that to reach the 'net-zero' target by 2050, Italy has to reduce them by more than 7% per year.
As the Mediterranean is one of the most subject to warming areas (‘a hot spot’), with an average warming that is twice as much as the global warming (thus about 3.0oC since the pre-industrial level) it should be one of Italy’s top priorities to support the efforts to reduce global emissions very fast, and lead by example. Failure to do so, will increase the negative impacts of climate change on this region, Italy included. Climate projections reported in the IPCC 6th Assessment Report indicate for Italy an increase in the probability of more frequent and intense heat waves (with negative impacts on health), summer droughts (with negative impacts on agriculture/livestock) and fewer but heavier precipitation events (with an increased number of floods), a faster melting of the Alpine glaciers (with negative impacts on water access), and an increased net immigration of climate refugees.
There is not a safe level of global warming. The more we consume fossil fuels, the more we emit greenhouse gases, the warmer the globe gets, and the more intense the damages are going to be, especially on the communities that have less resources to adapt to climate change".
(*) Full professor of Physics of the Earth System, Planets, Space and Climate, Interdisciplinary Research Centre for Sustainability and Climate at the Sant'Anna School.
