Friday, December 3

there is no doubt that climate change is caused by man




The new warning from the UN climate experts is clear and forceful. The climate change is “unequivocally” caused by humans and unprecedented in thousands, and even hundreds of thousands, of years. Record temperatures every year, droughts, torrential rains, fires that are no longer extinguished, increasingly powerful hurricanes … No part of the planet is free from the consequences and the alterations are so profound that their effects, such as the increase in the level of the sea ​​or thaw, will also be irreversible for hundreds or even thousands of years.

The Intergovernmental Panel on Climate Change (IPCC), made up of hundreds of the world’s leading climate scientists, has analyzed 14,000 studies over the past few years to provide a scientific basis solid to climate policies. It is in this report, ‘The Foundation of Physical Science’, that the debate on whether human activity is behind it is completely settled of global warming. For the first time, the 195 countries that make up the organization have agreed that it is an “unequivocal” fact. “The debate is closed, but not because the IPCC says so, but because there is no scientific basis” that provides evidence to the contrary, explains to ABC José Manuel Gutiérrez, one of the authors of the report and deputy director of the Institute of Physics of Cantabria (IFCA).

The evidence that man is causing the rise in temperatures, through emissions of greenhouse gases such as CO2, is already overwhelming. With global warming that is currently 1.1ºC over pre-industrial times, everything points to the fact that, in the next 20 years, the global temperature will reach or exceed 1.5 ° warming, even if emissions are drastically reduced. This was the first threshold that the world should avoid crossing, as agreed by 195 countries in the Paris Agreement. Going through it will lead to increasing heat waves, more droughts and shorter cold seasons, among other consequences.

Avoid 2 degrees

But it will be even more serious in case of arriving at 2nd, a line that scientists consider review, since from here the changes in the climate will be exponential. This scenario will also be reached throughout the 21st century if emissions do not begin to be reduced in a rapid, widespread and profound way, implementing objectives such as net zero emissions.

Thus, scientists leave the door open to hope, since they consider it possible to avoid the worst consequences of climate change, but the call made by the report is serious. Failure to do so will result in extreme hot temperatures being reached more frequently. up to critical tolerance thresholds for agriculture and health, the report shows.

For example, the intensity of agricultural droughts that previously occurred once every 10 years in dry regions, under a 2 degree scenario will occur more than twice as often, and will be even harsher. Or days with extreme temperatures that previously occurred once every 50 years will be up to 13 times more frequent, with records that will also be 2.7 degrees higher than they already were. And if so far the sea level has risen by about 20 cm since 1900, if global temperatures rise 2 degrees, the level of the oceans will rise about half a meter in the 21st century. And it will continue to rise to nearly two meters by 2300, double what the IPCC predicted in 2019.

«The stabilization of the climate will require strong, rapid and sustained emission reductions of greenhouse gases, and reach zero net CO2 emissions. Limiting other greenhouse gases and air pollutants, especially methane, could have both health and climate benefits, ”says IPCC Working Group I Co-Chair Panmao Zhai.

Lasting effects

The starting point is not good. In 2019, atmospheric carbon dioxide concentrations were higher than at any time in at least 2 million years, and the concentrations of methane and nitrous oxide were higher than at any time in at least 800,000 years. And these gases, capable of lasting for decades in the atmosphere, will continue to accumulate in the coming years, warming the planet and maintaining some of the effects of climate change.

Among the alterations that will take centuries or even millennia to reverse, and only if emissions are reduced, is the rise in sea levels, melting or acidification of the ocean. Coastal areas will see a continuous rise in sea level throughout the 21st century, which will contribute to more frequent and severe coastal flooding in low-lying areas and coastal erosion. Extreme sea level events that previously occurred once every 100 years could occur every year at the end of this century. Furthermore, further warming will amplify the melting of permafrost (the permanently frozen ground) and the loss of seasonal snow cover, the melting of glaciers and ice sheets, and the loss of Arctic sea ice in summer.

Also changes in the ocean, including warming, more frequent marine heat waves, ocean acidification and reduced oxygen levels, have been clearly linked to human influence. These changes affect both ocean ecosystems and the people who depend on them, and will continue for at least the rest of this century. While in regard to the rain patterns, at high latitudes, precipitation is likely to increase, while it is expected to decrease in large parts of the subtropics.

Interactive atlas

Furthermore, for the first time, the Sixth Assessment Report provides an more detailed regional assessment of climate change, which includes useful information for risk assessment, adaptation and decision-making. Coordinated by a Spanish team, the information is published in an Interactive Atlas
. “It is also the first time that everything has been done in the open,” admits Gutiérrez. In a massive effort, the new framework helps translate physical changes in the climate system into their effects – heat, cold, rain, drought, snow, wind, coastal flooding, and more – what they mean for society and ecosystems.

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