October 20, 2021

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“Extreme Warning”: What to remember from the IPCC report on climate

Three years of work, two hundred and thirty writers from sixty countries, reviewed fourteen thousand scientific publications, which generated 78,000 comments by several thousand critics …

The Intergovernmental Panel on Climate Change (IPCC) has published an updated assessment of knowledge about the impact of human activities on climate and the risks associated with it. A Titanic job paints a dark picture.

Zero suspicion

For those still skeptical, the responsibility for human action on climate change – and more precisely the greenhouse gas emissions released into the atmosphere since the beginning of the Industrial Revolution in 1750 – “Ambiguous” In the view of IPCC experts.

Rapid and widespread changes have taken place in the atmosphere, oceans, cryosphere and biosphere., They point out, changes in atmospheric circulation, melting of glaciers and glaciers, sea acidification, increased rainfall or changes in the distribution area of ​​marine and terrestrial animal species …

Based on data from an earlier report, since 2011 the concentration of these gases in the atmosphere has been steadily rising as expected, with both CO2 (which now averages 410 parts per million, which was less than 400 ppm ten years ago) exceeding methane or nitrous oxide. .

Over the past sixty years, this effect has been mitigated by the role of “carbon sink” played by land and ocean, which absorbs about 56% of carbon dioxide emissions annually. But if nothing is done to change the course this buffer effect is likely to decrease drastically in the future.

The report further notes that each of the last four decades has been hotter since 1850 than all the previous decades. As a result, the planet gained about 1.1 C during the period 1850-1900, for which there is extensive universal data to estimate the temperature of the Earth’s surface.

Since the 1970s, the ocean’s crust has warmed (0 to 700 m) and acidification has increased, while oxygen levels have decreased. The world average sea level increased by 20 cm between 1901 and 2018, increasing its speed from 1971 to 3.7 mm per year now.

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The authors note that the global average rainfall may have increased since the 1950s. This phenomenon seems to have accelerated since the early 1980s. Each time, the involvement of human activities raises a slight suspicion. Without being the only one, they are often the main factor.

Unprecedented for thousands of years

In short, ” Human influence has warmed the climate like never before for at least the last 2,000 years “, Summarize IPCC Experts.” This is an established fact This is undeniable, French paleoclimatologist Valerie Mason-Delmot, co-chair of the scientific team that wrote this document, comments.

Disorders of the climatic system are reflected in extreme weather and climatic events in all residential areas of the world: heat waves, torrential rains, droughts, tropical cyclones, etc. Frequent but severe events. Evidence of human responsibility, again, has been strengthened, scientists argue, linking monsoon disruptions to others, “It plays a major role in two – thirds of the world’s population.”, Recalls Valérie Masson-Delmotte.

To facilitate access and understanding of this information, the report is first linked to an interactive atlas that displays data taken into account at a regional level and linkes the extent to which this data should be measured. Changes affect different parts of the world in many ways.

A chance again

According to recent predictions, doubling the CO2 concentration in the atmosphere will increase the thermometer in the range of 2.5 to 4.5 ° C, with the best rating being 3 ° C.

Climate researchers consider the evolution of climate according to five emission conditions, from the most virtuous to the most catastrophic. However, temperatures on the Earth’s surface will continue to rise until at least the middle of the century.

Under the most active conditions of massive reductions in CO2 emissions and other greenhouse gases in the coming decades, the international community can reach the goal of surpassing the 1.5 ° C limit and temporarily surpassing even one tenth. A degree over the next twenty years, before returning to 1.4 C at the turn of the century. In the worst case scenario, in thirty years we will be at +2.4 degrees, resulting in great difficulties.

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If we reduce immediately “Strong, fast and consistent These problems and benefits will be realized within ten to twenty years », Emphasizes Mrs. Mason-Delmott. Every tenth degree counts because the co-chair of the task force insists. “ Every part of the extra warming has very clear effects. It increases the duration, intensity and recurrence of serious events. The SongeComments That we live AjoR.Are today For many of them EnableAtAttached to the sizeuPlanetary fish. Heat waves that occur every 50 years in pre-industrial climates now occur 4.8 times more frequently. In a world one and a half degrees warmer, it is 8.6 times more, she explains. Another example: when the world temperature rises by two degrees, the number of days of drought in the Mediterranean region can almost double.

Breaking this vicious circle will ensure the evolution of these extreme phenomena and lead to the acidification of the ocean – at least on the surface. But for this, it is imperative to achieve net negative emissions, which must use methods to consistently retain a portion of the CO2 in the atmosphere. These methods should be used with caution because some of them can have a large impact on biochemical cycles and affect biodiversity, food production, water availability and quality internally.

Activation of methane emissions, the second most important contributor to global warming, forms an important lever for the process, with her part being Sophie Sofa, an expert in atmospheric chemistry and co-author of the report. This greenhouse gas actually has a much more powerful warming capacity than CO2, but has a much lower stability in the atmosphere (one hundred to ten years), so the benefits will be quickly realized. In addition, methane is a precursor to ozone, an air pollutant with significant health risks. So we will succeed in both things.

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Already irreversible effects

Whatever it is, some of the consequences of the processes that have begun may be irreversible in the short term. Even if the temperature remains at + 1.5 C, it will take some time for the glaciers to return to equilibrium. And he “It is almost certain that the global average sea level will continue to rise in XXIe Century “, The IPCC underlines. In the most promising situation where emissions will decrease without much delay, the world average sea level is likely to rise by 2100 by 28 to 55 cm. In a catastrophic situation where the emissions erupt happily, the uncertainty surrounding the behavior of the polar caps can flip two meters or more.

In the long run, sea levels are expected to rise for centuries as the deep oceans continue to warm and melt ice. The Will be thousands of years high “, The report adds, indicating that over the next 2000 years, if global warming is limited to 1.5 ° C, global average sea levels will rise by about 2 to 3 m.

In anticipation of the release of this report, British Minister Alok Sharma, Chartered Accountant and future President of the United Nations Climate Conference (COP 26) in Glasgow in November, That said ” Human behavior is a very serious warning to accelerate global warming. “We can’t wait two years, five years Or ten Years ” To act, he continued. Betting (Re) Open …