Science already admits irreversible effects of climate change on the planet

Climate change, caused “undoubtedly” by human activity, has pushed the world into its warmest period in 2,000 years, and will have irreversible effects for millennia, warns a new report from the Intergovernmental Panel on Climate Change (IPCC).

The IPCC document, which since 1988 has analyzed for the United Nations the effects of climate change on the planet, indicates, for example, that mountain glaciers and at the poles will continue to melt for decades or even centuries, even reducing emissions.

“The report is a reality check. We now have a much clearer vision of the past, present and future climate, which is essential to understanding where we are going, what we can do, and how we should prepare,” valérie Mason-Delmotte, co-chair of the think tank that drafted it, said in introducing the report.

The paper also foresees irreversible thousand-year-scale changes in ocean temperature, acidification and deoxygenization.

On the other hand, it predicts that sea level will continue to rise irretrievably, between 28 and 55 centimeters by the end of the century with respect to current levels even achieving net zero emissions.

“For decades the IPCC has warned us of the dangers of global warming, the world listened but did not act forcefully enough, and as a result the problem is here and no one is safe,” said Inger Andersen, executive director of the UN Environment Programme.

THE HOTTEST WORLD OF THE LAST TWO MILLENNIA

The report says that humans have played an “undeniable” role in warming the atmosphere, ocean and soil, leading the world to a rise in temperatures that is unparalleled in the last 2,000 years.

The study, which takes advantage of improvements in paleoclimatic research, shows that the current temperature increase is comparable to what is so far considered the warmest period of the last 100,000 years, which occurred 6,500 years ago (the so-called Holocene climate maximum).

“It is indisputable that human activities have caused climate change and cause extreme weather events to be more frequent and severe, affecting all regions of the planet,” said IPCC Chair Hyesong Lee.

“Using a sporty simile, the atmosphere is ‘doped’, and we now suffer from these phenomena more frequently, as we have recently seen with the fires in Greece and California, or the floods in China and Europe,” added the Secretary-General of the World Meteorological Organization (WMO), Petteri Taalas.

The current changes in the climate are “unprecedented” in recent centuries and even millennia, say the scientists who authored the report.

For example, according to IPCC experts, the current concentration in the atmosphere of carbon dioxide, the main greenhouse gas, exceeds 410 particles per million, the highest in the last two million years.

Experts calculate in the report that if the current rate of greenhouse gas emissions is maintained, the global temperature will increase by 2.7 degrees by the end of the century compared to the average of the pre-industrial era (1850-1900).

This increase, which would also lead to greater extreme weather events such as droughts, floods and heat waves, would be far from the target of less than 2 degrees set by the Paris Agreement, which even called for limiting that rise to 1.5 degrees Celsius.

The new report from the main institution that studies climate change, delayed several months due to the covid-19 pandemic, considers five scenarios, depending on the level of emissions that is reached.

Maintaining the current situation, in which the global temperature is on average 1.1 degrees higher than in the pre-industrial period (1850-1900), would not be enough: scientists predict that this would reach an increase of 1.5 degrees in 2040, 2 degrees in 2060 and 2.7 in 2100.

FOUR DEGREES MORE, CATASTROPHIC SCENARIO

In the most pessimistic scenario, where emissions of carbon dioxide and other greenhouse gases doubled by mid-century, the increase could reach catastrophic levels of around 4 degrees by 2100, the report warns.

Each degree of increase could mean 7% more rainfall in the world, which would lead to an increase in storms, floods and other natural disasters.

Extreme heat waves, which in pre-industrial times occurred about once a decade and currently occur 2.3 times, could multiply up to 9.4 times (almost once per year) in a scenario with 4 degrees more temperature.

On the contrary, in the most optimal scenario considered by the report, the one in which carbon neutrality (net zero emissions) is reached by mid-century, the temperature increase would be 1.5 degrees in 2040, 1.6 degrees in 2060 and would even fall to 1.4 degrees by the end of the century.

“Stabilizing the climate will require strong, rapid and sustained reductions in greenhouse gas emissions, to reach net-zero emissions,” said another co-chair of the think tank, Panmao Zhai.

The study, prepared by 234 authors from 66 countries, acknowledges that reducing emissions would not have discernible effects on global temperature until about two decades later, although the benefits in air pollution would be noticed earlier, in a matter of a few years.

This document, focused on the scientific basis of climate change, will be complemented in 2022 by two others carried out by other IPCC working groups (one focused on the adaptation of societies and the other on mitigation measures).

The three will serve to synthesize the ipcc’s sixth general report, scheduled for September 2022, to continue the work begun in 1990, 1995, 2001, 2007 and 2014.

Source: EFE