The Landmark assessment shows that greenhouse gases clearly promote extreme weather, but countries can still avoid the worst effects. According to a landmark report on the state by the United Nations, modern society’s continued dependence on fossil fuels is heating the world at an unprecedented rate in the past 2000 years, and its impact is already evident because of record droughts, wildfires, and floods.

To communities all over the world. Climate science. The United Nations Intergovernmental Panel on Climate Change (IPCC) assessment shows that if greenhouse gas emissions continue, the situation will worsen. The future of the planet depends to a large extent on the decisions that humans make today.

“Evidence is everywhere: if we don’t take action, things will get very bad,” said Zhang Xuebin, a climatologist with Environment Canada in Toronto, Ontario, and the coordinating lead author of the report, which was published on August 9.

The report was prepared by more than 200 scientists within a few years and was endorsed by 195 governments at a virtual meeting last week. It is the first of three reports to assess the state of climate change and efforts to mitigate and adapt to climate change. share. The document is part of the IPCC’s sixth climate assessment since 1990, less than three months before the next major global climate summit to be held in Glasgow, UK. There, the government will have the opportunity to work to reverse the situation and reduce emissions.

If global emissions reach net zero around 2050, a goal that many countries have committed to last year, the world can meet the targets set in the 2015 Paris Agreement and limit global warming to less than industrialization. The previous level is within 1.5 ° C. Said Valérie Masson Delmotte, a climatologist at the Gifsur Yvette Environmental and Climate Sciences Laboratory in France and co-chair of the physical sciences working group that wrote this report. “The climate we experience in the future depends on our current decisions,” he said.

It’s Getting Hot In Here!

Compared with the average level from 1850 to 1900, the temperature of the earth’s global surface has risen by approximately 1.1°C, a level that has never occurred in the 125,000 years before the last ice age. This is just one of the hard facts that appeared in the summary released with the decision-makers IPCC report. The
overall assessment emphasizes efforts to determine how much temperature will rise if atmospheric emissions continue, and provides climate scientists with the most reliable predictions for the 21st century.

A key indicator used by researchers to make predictions is “climate sensitivity,” which is a measure of how much long-term warming is expected on the planet when the atmospheric carbon dioxide concentration doubles compared to pre-industrial levels. Although the IPCC’s best estimate is still 3°C, the report uses evidence such as ancient and modern climate records to reduce the uncertainty of this number, narrowing the possible range to 2.5-4°C. In contrast, the latest IPCC climate assessment report released in 2013 has a sensitivity range of 1.5–4.5 °C.

This reduction in climate sensitivity has strengthened scientists’ confidence in their predictions of what will happen on Earth under several different conditions. For example, according to the IPCC report, in a mild emission scenario with little change from today’s global development model, the global average temperature will rise by 2.1 to 3.5°C. This is much higher than the 1.5 to 2°C target limit set by the countries that signed the 2015 Paris Climate Agreement.

Even when the government is actively reducing greenhouse gas emissions, the report predicts that the global temperature may exceed the 1.5°C C threshold and then fall below that threshold again at the end of the century.

” Is it still possible to limit global warming to 1.5°C? The answer is yes, “said Maisa Rojas, lead author of the report and director of the Center for Climate and Resilience Studies at the University of Chile, Santiago.” But unless all greenhouse gases are reduced immediately, rapidly and on a large scale, global warming will be limited to 1.5 ° C is impossible to achieve. ”

Long Term, Extreme Impacts

The report lists a dizzying array of climate change impacts on the planet, and these impacts are already evident from pole to pole. Over the past decade, Arctic sea ice cover in late summer has been lower than it has been for at least 1,000 years. The continuing decline of global glaciers has been unparalleled for at least 2,000 years. The ocean is warming at a rate not seen since the end of the last ice age 11,000 years ago.

In addition to these thought-provoking measures, the IPCC report also highlights some of the most important scientific advances in understanding the regional impact of climate change, including places most affected by extreme heat, rainfall, and drought. For example, extreme drought has affected many regions of the world, especially the Mediterranean region and southwestern Africa.

Zhang said that as the temperature rises in the future, extreme weather events will become more and more serious. According to the report, if the earth’s temperature is 2°C higher than the pre-industrial temperature above the earth, then extreme temperature events that have occurred every 50 years in the past few centuries are likely to occur every 3-4 years. The world should also expect more complex events to occur simultaneously, such as heatwaves and prolonged droughts.
“We will not be hit by just one thing, we will be hit by several things at the same time,” Zhang said.

Permanent Changes 

According to the report, the effects of global warming on objects such as glaciers, ice sheets, and oceans will continue to be felt for centuries or even thousands of years, and these objects will slowly adapt to rising temperatures. It is estimated that the sea level around the world will rise by 2 to 3 meters in the next 2,000 years, even if the temperature is controlled within the heating range of 1.5°C, the sea level will rise by 6 meters when the temperature rises by 2°C. This will change the current residence of hundreds of millions of people on all coasts.

The report warns that some of the most serious effects of global warming cannot be ruled out, such as the collapse of ice sheets, massive loss of forests, or sudden changes in ocean circulation, especially when they have high emissions and significant warming at the end of the year. century. But he pointed out that the biggest uncertainty in all climate change predictions is how humans will act.