Giving advice on climate change, extreme weather phenomenas and human impact on global warming to managers is a difficult problem for climate scientists.

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Cape Town had to "count down" before "No Water Day". Source: webbcanyonchronicle.com

Hardly anyone could forget the summer of 2018: the Northern Hemisphere was in an unusually hot state; Japan claims record temperatures of an unexpected natural disaster; Europe bends before long heat waves with devastating wildfires in Greece. Drought abetted, wildfire spread in the western United States.

Friederike Otto, a climate modeler at the University of Oxford, UK, jumped when journalists questioned her assessment of the role of climate change in the summer heatwave of the summer of 2018. “ So crazy”she said. The common scientific feedback is that most heat waves will come more and more often by global warming. But Otto and his colleagues want to answer a more specific question: How does climate change affect heat waves? After conducting research on three-day calculation models, they announced: their initial analyzes for the Nordic region showed that climate change generated twice as much heat waves when it appeared in many other places.

Typically, journalists are more likely to receive quick analysis of weather agencies than from academic circles. With the support of Otto, the German weather forecast agency in Offenbach is preparing to become the first in the world to receive quick assessments about the connection of specific meteorological events to global warming. By 2020, the agency hopes to quickly publish its results to the media with public reports after a week or two of climate events. "We want to quantify the impact of climate change on any conditions of the atmosphere and can lead to extreme weather events in Germany and Central Europe," said Paul Becker, vice president of the German weather forecast agency says. "Science is old enough to start this up."

The EU is also interested in this issue. The European Center for Medium-Range Weather Forecast (ECMWF) in Reading, UK, is preparing to test a similar program in 2020 to study extreme weather phenomenas, such as heat waves or floods to human-induced climate change phenomenon. If all goes well, an EU service will be available at the site in the next one or two years, according to Richard Dee, who is in charge of the EU's Post-Copernicus Transformation Service at ECMWF. "This is an ambitious but feasible goal," Otto said. She is the one who is promoting this EU effort.

Weather forecasters are planning regular services to show how far the impact on climate change has been since the start of advanced research projects about a decade ago which tried to attribute separate weather phenomena to climate change. After 170 studies have been published in peer-reviewed journals, scientific competence has spread throughout the world. Although it is still difficult to explain some types of extreme weather events, meteorological services have begun to provide periodic information, the biggest challenge being how such studies can be useful for everyone.

Thousands of impacts on the climate

The idea behind simple scientific attribution is that it needs proof. Disasters such as heat waves exceed previous levels of record, extreme rainfall often becomes common because the formation of greenhouse gases is transforming the atmosphere. Warming air contains more water evaporating and accumulating more energy; Increased temperatures can alter atmospheric circulation patterns. But extreme weather phenomenon can increase from natural cycles such as the El Niño phenomenon that occurs periodically when temperatures warm the water surface in the tropical Pacific Ocean <

From 2004 to mid-2018, scientists have published more than 170 works addressing 190 extreme climate events around the world, according to an analysis by Nature. So far, the proposed studies: about two-thirds of the extreme climate events that have been studied are likely to result from ever-increasing human-induced climate change. Extreme heat events account for more than 43% of these events, followed by drought (18%) and extreme rain or flooding (17%). In 2017, for the first time, studies even claimed three extreme events took place without the hands of climate change: heat waves in Asia in 2016, global record heat levels of the year. That is, the sea warmed up in Alaska Bay and Bering Sea from 2014 to 2016. But 29% of the cases in Nature's analysis, the evidence that human impact on climate is not clear or stable enough. Let the scientists make a judgment.
Surveys have shown that people tend to respond to climate change impacts when they experience extreme weather events, so it is important to quickly identify the link between events occurring in an area with climate change to be effective.

As deputy director of the University of Oxford's Institute for Environmental Studies, Otto has extensive experience in cases like these. For example, in June 2018, she and her colleagues completed a study focusing on the southern edge of South Africa, which had suffered from drought for three consecutive years, which became increasingly harsh to the Western Cape in the South. So much so that the Cap Town government has warned it could soon come to "No Water Day" when the water level of dams supplying the city drops below 13.5% and the whole region may not have enough water for both necessities, the first thing that happens to a big city.

Prior to the "No Water Day" reports, Otto and Mark New, a climate scientist at the University of Cape Town, came to the conclusion that the event was a good example of the study of the findings. Human responsibility to the climate. Taking advantage of the rare free time, researchers from the Netherlands, South Africa, the United States and the United Kingdom began this "off-budget" project by looking at a long-term drought in Cape Town. They created an index of the severity of drought with measurements of rainfall and heat, then came to the main task of determining the role that humans play in drought: complex computational models. The magazine imitates the Earth's climate. Over five independent models exist, they perform thousands of simulations. Several models have taken into account the levels of anthropogenic greenhouse gases; There are models that represent the natural concentrations of greenhouse gases, in the absence of an industrial revolution.

By the time the team met in June 2018, the rain had returned to South Africa and "No Water Day" had left, but scientists were still pursuing the causes of a "super drought". because this could help them determine whether the area could face another similar disaster this time. Coordinating the Skype meeting from the Oxford office, Otto looked less stressed when his colleagues agreed that the analysis had yielded results. "Global warming has tripled the severity of three consecutive years of drought in this region," she said.

That discovery came just in time for Roop Singh, a climate risk consultant at the Red Crescent Center / International Red Cross in La Hague, the Netherlands, presenting the results at a conference. on responding to climate change in Cape Town. The researchers did not find shocking results, Singh said, but they sparked discussions about whether the severity of the drought could prove to increase investment and diversify sources. water in Cape Town or not. The research by Otto et al was published in Environmental Research Letters, a peer-reviewed open-access journal, and on the World Weather Attribution website, a collaboration of six research institutes including Oxford University. formed in 2014 to analyze and communicate the possible effects of climate change on extreme climate events.

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Map showing the heat wave in the summer of 2018 in Europe.

Although Cape Town avoided "No Water Day" in 2018, regional policymakers said the results of Otto's research gave a alert alert of water to regulators for them to be willing to reduce the risk of global warming. "This is a clear message that we cannot ignore," said Helen Davies, who is in charge of the green economy of the Tourism and Economic Development Board, the Western Cape government. "Maybe we can basically take a new approach in water management."

Sometimes, some studies have conflicting conclusions about a specific event. A study of heat waves in Russia in 2010 found a link between its severity and the normal fluctuations of nature, another analysis that identified climate change as likely to create events. there. The press was confused about the results, but climate researchers were not too surprised by this difference because the two studies looked at different issues: the severity of the event and the frequency of the occurrence. According to Otto, "this example shows that shaping information to communicate questions about human impact on the climate is a real challenge." But since then, researchers have also become wiser about how to set up and present research, she adds.

The effects are not clear

In South Africa, Davies said Otto's new study could help underline the case of Cap Town with new approaches to regional water management. “Meteorologists once said that they were tied to us after the second year of drought, there is no chance for a third consecutive drought ... But what continues to happen in the third year of drought, we can't apply what the past to the future will come. We need to learn how to respond to a changing climate. ” One of the lessons from the drought they experienced and the analysis of the impact of humans on the climate is that the water supply to the Western Cape cannot depend on each rainfall but need additional supplies, she said. As an alternative, it may be necessary to diversify with groundwater and expand desalination and wastewater treatment.

But overall, it's hard to know the effectiveness of studies on human impacts on climate, from the perspective of social scientists. Because it's hard to point out the effects of the findings from those studies, which are predicted to increase risks when extreme weather starts to change climate - or from the very shock of the people themselves. Extreme weather events. If those studies were accompanied by weather reports rather than appearing in specialized scientific journals, then the impact of the information would be much more noticeable, according to Jörn Birkmann, an expert on regional planning and space at the University of Stuttgart, Germany. "City and infrastructure planners need to carefully consider the risks of extreme weather events if they are clearly involved in climate change," he said.

Not all studies of human impact on climate are certain, Hegerl commented. Algorithms still need to be refined to model many local storms. Because storms result from air convection like small hail storms and tornadoes, scientists cannot determine whether climate change has created such events. Human impacts on climate are in fact very complex or even impossible because there are places where there is a lack of long-term climate profiles such as African countries.

Source: Sunllight