Modern society’s continued dependence on fossil fuels is warming the world at an unprecedented rate in the past 2,000 years-its impact is already evident as record droughts, wildfires and floods have destroyed communities around the world-according to a report United Nations landmark report on the state of climate scienceThe assessment of the United Nations Intergovernmental Panel on Climate Change (IPCC) shows that if greenhouse gas emissions continue, the situation may get worse, but it also clearly shows that the future of the planet depends to a large extent on what humans do today choose.
“Evidence is everywhere: if we don’t take action, things will get very bad,” said Zhang Xuebin, a climatologist with Environment Canada in Toronto and the coordinating lead author of the report, which was released on August 9.
The report was prepared by more than 200 scientists over a period of several years, and was approved by 195 governments at a virtual meeting last week. It is the first of three reports that will assess the impact of climate change. Status and efforts to mitigate and adapt to climate change. This document is part of the IPCC’s sixth climate assessment since 1990, less than three months before the next Global Climate Summit in Glasgow, Scotland. There, the government will have the opportunity to make commitments to change direction and reduce emissions.
If global emissions reach net zero by the middle of this century—a promise made by many countries in the past year—the world can achieve the goals set by the 2015 Paris Agreement and limit global warming throughout the process Within 1.5 degrees. In the 21st century, said Valérie Masson-Delmotte, a climatologist at the French Gif-sur-Yvette Climate and Environmental Science Laboratory and co-chair of the Physical Science Working Group that prepared the current report. “The climate we experience in the future depends on our current decisions,” she said.
Compared to the average level between 1850 and 1900, the earth’s global surface temperature has increased by approximately 1.1 °C, a level that has not been seen since before the last ice age about 125,000 years ago. This is just one of the straightforward facts that appeared in the summary published with the IPCC report and used by decision makers.
The overall assessment emphasizes efforts to determine how much temperature will rise if atmospheric emissions continue, and provides climate scientists with The most confident prediction to date In the course of the 21st century. A key indicator used by researchers to make predictions is “climate sensitivity,” which is a measure of the long-term warming of the earth caused by the doubling of atmospheric carbon dioxide from pre-industrial levels. Although the IPCC’s best estimate is still 3 °C, the report uses evidence such as modern and ancient climate records to reduce the uncertainty of this number, narrowing the possible range to 2.5-4 °C. In contrast, the last IPCC climate assessment report released in 2013 had a sensitivity range of 1.5–4.5 °C.
The shrinking climate sensitivity has strengthened scientists’ confidence in their predictions of what will happen on Earth under many different scenarios. For example, according to the IPCC report, in a mild emission scenario with little change in the current global development model, the global average temperature will rise by 2.1-3.5°C. This is much higher than the 1.5-2°C limit set by the countries that signed the 2015 Paris Climate Agreement. Even when the government is actively cutting greenhouse gas emissions, the report predicts that the global temperature may exceed the 1.5°C threshold in the next few years and then fall below that threshold by the end of the century.
“Is it possible to limit global warming to less than 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 in Santiago. “But unless there is Immediate, rapid and large-scale cuts Of all greenhouse gases, limiting global warming to 1.5°C would be out of reach. “
The report lists a dizzying array of impacts of climate change on the planet-and these impacts are already evident from the poles to the poles. Over the past 10 years, the Arctic sea ice coverage in late summer was lower than at least 1,000 years. The continuous global glacier retreat has been unparalleled for at least 2000 years. The ocean is also heating up at a rate not seen since the end of the last ice age 11,000 years ago.
In addition to these thought-provoking measurements, the IPCC report also highlights some of the most important scientific advances in understanding the regional impact of climate change, including the places most affected by extreme heat, precipitation, 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 reaches 2°C higher than the pre-industrial temperature on land, extreme temperature events that have occurred every 50 years in the past few centuries may occur every four years. The world should also expect more complex events, such as simultaneous heat waves and prolonged droughts.
“We will not be hit by just one thing, we will be hit by many things at the same time,” Zhang said.
According to the report, the effects of global warming on objects such as glaciers, ice caps and oceans will continue for hundreds or even thousands of years. They have not yet fully adapted to the current level of warming, let alone higher temperatures in the future. It is estimated that in the next 2,000 years, the sea level will rise by 2-3 meters, even if the temperature stays at 1.5 °C and rises to 6 meters at 2 °C, this will change the entire coastline that is currently inhabited by hundreds of millions of people.
The report warns that some of the most serious climate impacts cannot be ruled out, such as the collapse of ice sheets, massive loss of forests, or sudden changes in ocean circulation, especially when emissions are high and climate warming is nearing the end. century. But it pointed out that the biggest uncertainty in all climate change predictions is how humans will act.
For thirty years, the IPCC has been warning of the dangers of global warming, but governments have not yet taken the necessary actions to transition to clean energy and stop greenhouse gas emissions. But maybe things are about to change, Zhang said, this is only because people around the world are beginning to see the impact of climate change on their surroundings.
“Climate change is happening and people do feel it,” Zhang said. “The report only provides scientific verification to the public. Yes, your feelings are actually true.”
But the IPCC report also pointed out something more important: If we take positive action now, many of the most terrible effects of climate change can still be avoided. Rojas said that every degree of warming is important. “This is a very powerful idea,” she said. “The future is in our hands.”
This article is reproduced with authorization and has been First published August 9, 2021.