In a first study of Pakistan’s floods, scientists see climate change at work

By Raymond Zhong

Pakistan began receiving abnormally heavy rain in mid-June, and, by late August, drenching downpours were declared a national emergency. The southern part of the Indus River, which traverses the length of the country, became a vast lake. Villages have become islands, surrounded by putrid water that stretches to the horizon. More than 1,500 people have died. Floodwaters could take months to recede.

The deluges were made worse by global warming caused by greenhouse-gas emissions, scientists said Thursday (15), drawing upon a fast-growing field of research that gauges the influence of climate change on specific extreme weather events soon after they occur — and while societies are still dealing with their shattering consequences.

As climate scientists’ techniques improve, they can assess, with ever-greater confidence and specificity, how human-induced changes in Earth’s chemistry are affecting the severe weather outside our windows, adding weight and urgency to questions about how nations should adapt.

The floods in Pakistan are the deadliest in a recent string of eye-popping weather extremes across the Northern Hemisphere: relentless droughts in the Horn of Africa, Mexico and China; flash floods in West and Central Africa, Iran and the inland United States; searing heat waves in India, Japan, California, Britain and Europe.

Scientists have warned for decades that some kinds of extreme weather are becoming more frequent and intense as more heat-trapping gases get pumped into the atmosphere. As the planet warms, more water evaporates from the oceans. Hotter air also holds more moisture. So storms like those that come with the South Asian monsoon can pack a bigger punch.

But Pakistan’s monsoon rains have long varied wildly from year to year, which made it hard to pin down precisely how much more severe this season was because of climate change, the authors of the new study said. Still, most of their computer models indicated that human-caused warming had intensified the rainfall to some extent, convincing them that it was a contributing factor.

The country might have experienced disastrously high rainfall this year even without global warming, said the study’s lead author, Friederike Otto, a climate scientist at Imperial College London. “But it’s worse because of climate change,” Otto said. “And especially in these highly vulnerable regions, small changes matter a lot.”

The study was produced by 26 scientists affiliated with World Weather Attribution, a research initiative that specializes in rapid studies of extreme events. This year, scientists with the group found that the heat that scorched India and Pakistan this spring had been 30 times as likely to occur because of greenhouse gas emissions. July’s extreme heat in Britain had been at least 10 times as likely, the group found. Next up is a study on this summer’s drought in Europe.

Attribution studies aim to link two distinct but related phenomena: climate and weather.

Climate is what happens to the weather over long periods and on a planetary scale. Direct weather records only go back a century or so in many places, which is why scientists use computer models and concepts from physics and chemistry to build out their understanding of the evolving climate. But the weather has always been variable, even without the influence of human activity. Attribution studies try to separate this natural variability from the larger shifts that fossil-fuel emissions are bringing about.

Attribution research “really helps us understand how weather sits within long-term climate change,” said Daithi A. Stone, a climate scientist with New Zealand’s National Institute of Water and Atmospheric Research.

To perform an attribution, scientists use mathematical models to analyze both the world as it is and the world as it might have been, had humans not spent decades pumping planet-warming gases into the atmosphere. With computer simulations, they can replay recent history dozens, even hundreds, of times in both worlds to see how often the event, and others like it, occur in each. The differences indicate how much global warming was likely responsible.

Researchers often perform this comparison using scores of climate models to ensure their conclusions are sound. They also check the simulations against records of actual events that have occurred in the past.

To examine this year’s flooding in Pakistan, the authors of the new study looked at two metrics: the maximum 60-day rainfall each year between June and September over the entire Indus River Basin, and the maximum five-day rainfall each year over the badly hit southern provinces of Sindh and Baluchistan.

The researchers found that several of their models did not realistically reproduce patterns in the actual rainfall data for Pakistan. And those that did gave divergent answers for how much more intense and more likely this year’s rainfall had become under present levels of global warming.

The models gave clearer answers when considering a higher level of warming, however. This gave the researchers confidence to say that climate change had probably made this year’s flooding worse, though they refrained from estimating by how much.

Recent improvements in the climate models helped the authors narrow their estimates, Otto said. “The uncertainty bars are smaller than they would have been five years ago,” she said, referring to the lines in statistical charts that show ranges of possible values. “But monsoon is still something that models really struggle with.”

Pakistan’s highly varied topography, from its southern coast to the high Himalayan peaks in the north, causes its climate to be shaped by many physical drivers, said another author of the study, Fahad Saeed, a climate scientist based in Islamabad with the research group Climate Analytics.

“The representation of all these processes can get tricky when you’re applying a climate model,” Saeed said.

Scientists often find storms, droughts and wildfires tougher to attribute to global warming compared with extreme hot or cold spells. Those events involve not just temperatures, but also the circulation of air and complex interactions between land, sea and atmosphere. Even so, new and improved models, plus greater quantities of data, are helping to close the gaps.

“For us as climate scientists, our laboratory is our climate models,” said Andrew Hoell of the National Oceanic and Atmospheric Administration in Boulder, Colorado. “And they’ve advanced in ways that have allowed us to do more-robust attribution studies.”

Today, models are continuing to get better at capturing weather and its drivers at progressively smaller scales, Hoell said. Scientists can start to think not just about drought over a large area, but evaporation in specific watersheds and reservoirs. Not just average rainfall, but individual tornadoes and thunderstorms.

Climate scientists have also begun using artificial intelligence and other computational techniques to scour weather data for new insights, said Dim Coumou, a climate researcher at the Dutch university VU Amsterdam. These methods can help scientists uncover the hidden mechanisms that drive complex weather patterns, leading to better attributions and forecasts of extreme events.

“There is just a lot of data that is getting more accessible for scientists,” Coumou said.

Weather records show that South Asia’s monsoon is whipsawing more between drier years and wetter ones — unwelcome news for farmers who must increasingly deal with either parched fields or inundated ones.

Anders Levermann, a physicist at the Potsdam Institute for Climate Impact Research in Germany, has proposed one explanation. The South Asian monsoon begins each spring when the land warms and draws in moisture-rich air from the Indian Ocean. When this air hits the mountains and cools, its cargo of vapour condenses into rain and, in the process, releases heat. The heat draws even more air toward the land from the sea, which keeps the monsoon going.

On a warmer planet, there is more moisture in this system, which means the rains are amplified. But if anything blocks this inflow, such as an atmospheric disturbance or heavy air pollution, then its weakening effects on the monsoon might also be amplified, Levermann said.

“That’s the bad thing about climate change,” he said. “It’s not just an increase in something or a decrease in something. It’s an increase in variability.”

-New York Times

 

 

Comments are closed, but trackbacks and pingbacks are open.

otc high blood pressure treatment blood pressure guidelines medications blood pressure pills that is safe for the liver high blood pressure medication levothyroxine blood pressure medication that reduces blood pressure is there any difference in blood pressure pills high blood pressure child medication blood pressure medication recommendation nose blue blood pressure medication blood pressure is 150 68 should i take my medication blood pressure medication while nursing taking a bunch of high blood pressure pills aerobic exercise and blood pressure medication good blood pressure medication acupuncture treatment for low blood pressure best over the counter pills for high blood pressure blood pressure pill amlodipine besylate high blood pressure signs and treatment moderna vaccine blood pressure medication which blood pressure drugs do not cause tinnitus blood pressure medication fights cancer blood pressure medication skin rash side effects of high blood pressure medication impotence medication to avoid on blood pressure medications high blood pressure rx medication peripheral neuropathy caused by blood pressure medication high blood pressure in pregnancy treatment nice runny nose do to blood pressure medication how to get off of blood pressure pills hiv medication and high blood pressure niacin treatment for high blood pressure two drugs for blood pressure that caused cancer high blood pressure causing medications high blood pressure medication names canada blood pressure medication side effects alcohol i take 3 blood pressure medication blood pressure pills that help with anxiety what iv drug raises blood pressure list of doctors who formulated blood pressure medications how to remember blood pressure medications sleeping pills blood pressure how fast does blood pressure medication take effect sweet n low high blood pressure medication home treatment for blood pressure high blood pressure medication matrocet high blood pressure medication doses blood pressure drug bystolic iberstaron blood pressure medication blood pressure medications st alphabetical celexa and high blood pressure medication does blood pressure pills irritation skin can i take combivent with high blood pressure medication blood pressure medications beta blockers list what to do if blood pressure medication does not work drugs to lower your blood pressure red beet pills for blood pressure taurine and blood pressure medications how ling for garlic pills to lower blood pressure blood pressure medication list and side effects can i take aspirin with high blood pressure medication blood pressure medication teaching about hot tubs water pills high blood pressure over counter what is an arb medication for blood pressure resveratrol high blood pressure medication high blood pressure medication and weight loss gum disease and blood pressure medication benzenesulfonic acid in blood pressure medication taking two blood pressure pills by mistake allergy pills for high blood pressure blood pressure prescription drugs safety blood pressure medication in pregnancy trazodone and blood pressure medication which blood pressure medication is linked to skin cancer list of blood pressure medications with the least side effects could blood pressure medication make blood thicker disadvantages of high blood pressure medication blood pressure medications ludipril typical drugs for high blood pressure otc water pills for high blood pressure blood pressure medications that do not doncause bowel blockage high blood pressure after corrosion treatment how soon does high blood pressure medication work blood pressure medication teaching amertyrine high blood pressure medication increased blood pressure and heart rate after drug overdose over the counter drugs high blood pressure blood pressure medication 25 is blood pressure medication a nitrate most effective blood pressure pills blood pressure medical does red yeast rice interfere with high blood pressure medication can apple cider vinegar pills lower blood pressure does blood pressure medication give you headaches high blood pressure medication and driving should you take blood pressure pills with food inn blood pressure drugs can you eat bananas if taking blood pressure medication popular high blood pressure medication blood pressure medication los blood pressure medication second drug low blood pressure and hypertension medication do water pills lower blood pressure high blood pressure pill aqunadine high blood pressure cholesterol medication how does medication lower blood pressure acetaminophen blood pressure medication blood pressure medication 30 mg that works around the heart what does grapefruit do to blood pressure medication can red yeast rice be taken with blood pressure medication pharmaceutical treatment for high blood pressure are blood pressure pills statins blood pressure pills that start with r blood pressure medication and male impotence taking baby aspirin with other high blood pressure medications what is the medical name for a blood pressure cuff leg cramps and blood pressure medication blood pressure pill name starts with p natural high blood pressure treatments blood pressure medication names losartan higher blood pressure with radiation treatment medical marijauna high blood pressure how to avoid medication for high blood pressure what time is best to take blood pressure medication medication for palpitations and high blood pressure latest news on blood pressure treatment what if i take two blood pressure pills does xanax interfere with blood pressure medication amlipan blood pressure medication vitamin e and blood pressure medication tell me the side effects of high blood pressure medication herbs pills to lower blood pressure blood pressure medication urge to urinate what medication will safely replace lisop as blood pressure medicine active ingredient in high blood pressure medication blood pressure medications cause adrenal tumors is biktarvy ok to take with high blood pressure medication alembic blood pressure medication sandoz blood pressure medication exercise high blood pressure medication grapefruit pills blood pressure treatment for high blood pressure at home blood pressure medication for patients with osa cycle on off blood pressure medication blood pressure drugs that do not cause heat sensitivity blood pressure medications that do not cause coughing what blood pressure medications do not cause rosacea pfizer blood pressure medication side effects do garlic pills really help lower blood pressure should i take medication for anxiety induced blood pressure treatment for uncontrolled blood pressure decongestant medication high blood pressure can stiff days be used with high blood pressure medication how long does it take medication to lower blood pressure what if i miss a blood pressure pill tribenzor high blood pressure pills law lawsuit 2023 treatment of sudden drop in blood pressure zoloft and blood pressure medication orange high blood pressure pill cancer blood pressure pill why cant people with high blood pressure take keto pills how long for blood pressure to go down mini pill should i get second opinion before taking blood pressure medication blood pressure erectile dysfunction medication high blood pressure medication m lot ben medical device lowers blood pressure puppy ate blood pressure pill are there medications for low blood pressure dod blood pressure medication is losartan a blood pressure pill combination drugs for blood pressure marijuana and blood pressure medication interaction blood pressure medication interactions with grapefruit can you eat bananas while taking high blood pressure medication steps before going on high blood pressure medication blood pressure medication when to cut down foods to avoid on blood pressure medication blood pressure medications depression blood pressure medication non beta blocker tattoos and high blood pressure medication what is the medications used to lower blood pressure quickly high blood pressure medication leg swelling blood pressure medication men in your 40s blood pressure medication wieight loss blood pressure medication hy can blood pressure medication lower blood sugar does blood pressure medication make you pee natural treatment high blood pressure during pregnancy can you take l arginine with high blood pressure medication what class of blood pressure medication can can blood pressure pills reduce appetite faa approved medication for high blood pressure high blood pressure medication during pregnancy best blood pressure medication for type 2 diabetes blood pressure and pain medication pain medication that does not affect blood pressure best high blood pressure drugs on the market if you take incorrect medications to lower blood pressure low blood pressure treatments does your body have to adjust to blood pressure medication why water pill for high blood pressure drugs for treatment of very high blood pressure during pregnancy can i drink grapefruit juice with high blood pressure medication can blood pressure pills make you feel cold high blood pressure medication that helps with weight loss amlodipine blood pressure drug blood pressure medication for infants varicose veins blood pressure medication life extension high blood pressure medication does tylenol interfere with blood pressure medication can i take diamox with other high blood pressure medications prestige medical blood pressure cuff calibration drugs used for high blood pressure chamomile tea and high blood pressure medication narcotics stored alongside blood pressure medications in does nutrigrove blood pressure pills work extremely low blood pressure treatment blood pressure medication for iga nephropathy blood pressure medication low side effects can i increase my blood pressure medication what is the best blood pressure medication to take drugs that cause increased blood pressure does biotin interfere with high blood pressure medication cani od on high blood pressure pills blood pressure medication that also helps with jerking blood pressure medication categories first line treatment of high blood pressure medication for low blood pressure in usa armour thyroid drug interactions blood pressure meds hepatitis c treatment high blood pressure high blood pressure arb drugs low blood pressure treatment with essential oils high blood pressure medication list for pregnancy blood pressure medication and snake venom blood pressure medication low dose liquid blood pressure medications ivf drugs and high blood pressure left my blood pressure medication does it matter when you take blood pressure medication can you take blood pressure pills twice a day privilin blood pressure medication how big are blood pressure pills once you start blood pressure medication can you stop diuretic in blood pressure medication what medication reduce blood pressure new blood pressure treatment prescribed home medications for high blood pressure blood pressure medication side effects forums taking blood pressure pills dizzy when bend over a lot blood pressure medication and nyquil cinnamon pills and high blood pressure temporary high blood pressure treatment single agent blood pressure medication blood pressure medication made in china fda approved medications to reduce blood pressure immediate treatment for high blood pressure at home best time to take blood pressure pills muscle loss on high blood pressure medication blood pressure medication when needed treat high blood pressure without medication blood pressure medication side effects for men cbd pills for high blood pressure blood pressure regulation without medication blood pressure medication and pre workout high blood pressure alzheimer disease and antihypertensive treatment miss blood pressure medication blood pressure pills suicide peaceful emergency drugs for low blood pressure common blood pressure medications in canada systolic blood pressure define medical viril and high blood pressure pills can statin drugs help lower blood pressure do you have to wean off blood pressure medication new drugs for blood pressure when is high blood pressure medication necessary drugs for hi blood pressure cold medications and blood pressure taking 2 blood pressure pills mistake why doctors stopped prescribing blood pressure medication common high blood pressure medication canada what side effects does blood pressure medication have ulcer medication high blood pressure can high blood pressure medication elevate alkaline phosphatase blood pressure medication warning getting blood pressure medication jamaica alkaline water and blood pressure medication blood pressure going up and down with medication drugs reduce systolic blood pressure treatment for rapid high blood pressure low blood pressure alternative treatment do all high blood pressure medications cause weight gain medication for increasing blood pressure blood pressure medication for african american males vitamins for high blood pressure treatment aleve with blood pressure medication how to lower blood pressure without pills blood pressure triple pill who blood pressure guidelines for hygiene treatment what drug reduces blood pressure blood pressure medications enalapril met blood pressure medication