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  • Longer fire seasons.

  • Stronger hurricanes.

  • More intense heatwaves and floods.

  • Across the world, climate events are getting more extreme.

  • And while there's little doubt that global warming is to blame,

  • proving that fault for specific weather events hasn't really been possibleuntil now.

  • An emerging field called extreme-event attribution is helping us measure and verify the relationship

  • between the climate crisis and extreme weather.

  • Not only does this have huge implications for predicting and modeling our planet's future,

  • but it could also help us better prepare for living in an increasingly extreme world.

  • For a long time, there was a distinction between climate and weather.

  • And the reality is, extreme events are where we most acutely feel the climate system.

  • It's critical that we understand how global warming is impacting the extremes.

  • Because that's where the impacts from climate change are being played out.

  • When we talk about the impacts of the climate crisis, we're really talking about distinguishing the influence of natural factors

  • from anthropogenic factors on Earth's climate cycle.

  • Basically, this means teasing apart Earth's natural climate cycles from human-caused climate change.

  • A way to begin doing this is to examine thefingerprintswe humans have left behind on Earth's climate.

  • For example, our ice core records tell us that CO2 levels have risen by almost 50% in the last 150 years,

  • and records show that since the industrial age began over a century ago,

  • many regions of the world have warmed by more than 1.5 degrees Celsius.

  • By matching both the observed and modeled patterns of Earth's climate,

  • scientists can positively identify thefingerprints'' associated with these changes.

  • Following the tracks of these fingerprints has helped scientists link climate change with more general trends,

  • like rising sea levels and global temperatures.

  • But verifying the role of human influence on specific climate events, like Hurricane Harvey or the California drought?

  • That's not as easy.

  • It's precisely this problem of attributing specific extreme weather events to climate change

  • that researchers like Dr. Diffenbaugh are working on.

  • While we can't yet say for sure that these events wouldn't have happened without climate change,

  • we can talk about the probability of them happeningand how those odds are changing.

  • By comparing our climate predictions with how things actually play out,

  • researchers can start to develop a real-world framework for posing and testing hypotheses.

  • But the work doesn't stop there.

  • Observational data can only tell us if there's a change in the intensity or frequency of an event;

  • it still can't tell us what caused those changes.

  • This is where computer modeling comes in.

  • We can't run experiments on the global climate system. We can't stick the climate system in a lab.

  • But we can say, our extreme event attribution framework predicts a probability

  • of record-setting heat over a region of Europe to be X percent,

  • and then we can wait and watch and see how often record-setting temperatures occur.

  • These computer models can use real-world climate influences, like how much CO2 is present in the atmosphere,

  • to create a more complete timeline of extreme events.

  • Or, they can create hundreds of hypothetical histories that span thousands of years to test our world against.

  • This allows researchers to look at the world without human-caused climate change,

  • and assess the probability of events happening.

  • By comparing the probability between Earths with and without climate change,

  • researchers can begin to quantify the changes in risk...

  • and test how much the frequency and magnitude of extreme events have changed over time.

  • Over the past decade, the emerging field of extreme event attribution has used these tools

  • to help researchers find strong evidence of climate change's relationship to changing events like heat,

  • as well as tropical cyclones, wildfires, sea ice coverage, and flooding.

  • By combining observational records with climate models and our growing knowledge of how

  • global warming affects Earth's natural processes,

  • we're also getting better at distinguishing between the roles that human influence on the climate system

  • and climate variability play in specific climate events.

  • Being able to attribute specific climate events to climate change is extremely useful on many fronts.

  • For one, it can help researchers develop better climate models that can then be used by governments

  • to inform climate action plans.

  • It can also help us better understand the impact we're having on the climate and be better equipped to brace for these impacts.

  • A lot of our infrastructure, a lot of our planning is, is designed around, statistical analyses

  • that assume stationarity in the climate system.

  • If the global warming that's already happened has already changed the odds of those extremes,

  • then everything that we've designed and built based on that, there's risk of those thresholds being exceeded.

  • The infrastructure in many communities, from sidewalks to levees to storm surge barriers,

  • is built and managed based on the probability of the recurrence of climatic extremes.

  • For cities sitting on a floodplain, the likelihood of a major flood happening in a given year

  • will often determine how resilient their levees and dams must be.

  • If a city uses the 100-year floodplain as its threshold,

  • that means that its levees and dams are built to anticipate the 1% chance that a major flood could happen in any given year.

  • But the probability of these thresholds being exceeded is changing,

  • and the fact is that too many communities just aren't adequately prepared.

  • Extreme events don't just affect and disrupt essential infrastructure.

  • They can have an outsized effect on public health, our food supply, and our global economy.

  • The idea is that by being better able to know what to expect from the climate crisis,

  • the world can brace for the worst while making informed decisions to stop the worst from happening.

  • We see it year after year in the US and around the world.

  • We're living with a world where unprecedented, extreme events are more likely. They're happening more often.

  • We're living with that now.

  • And the impacts of those extremes are growing the cost that we're bearing.

  • While extreme event attribution is helping us more confidently connect the dots between climate change

  • and individual weather events, it's still a very new field and there's a lot to learn.

  • Check out our video here on how scientists are modeling a world without clouds.

  • Don't forget to subscribe to Seeker, and as always, thanks for watching.

Longer fire seasons.

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B1 climate extreme climate change probability attribution global warming

Scientists Can Now Prove That Climate Change Is Causing Natural Disasters

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    林宜悉 posted on 2020/11/25
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