Sign up for our daily briefing

Make your busy days simpler with Axios AM/PM. Catch up on what's new and why it matters in just 5 minutes.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Catch up on the day's biggest business stories

Subscribe to Axios Closer for insights into the day’s business news and trends and why they matter

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Stay on top of the latest market trends

Subscribe to Axios Markets for the latest market trends and economic insights. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Sports news worthy of your time

Binge on the stats and stories that drive the sports world with Axios Sports. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Tech news worthy of your time

Get our smart take on technology from the Valley and D.C. with Axios Login. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Get the inside stories

Get an insider's guide to the new White House with Axios Sneak Peek. Sign up for free.

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Catch up on coronavirus stories and special reports, curated by Mike Allen everyday

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Denver news?

Get a daily digest of the most important stories affecting your hometown with Axios Denver

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Des Moines news?

Get a daily digest of the most important stories affecting your hometown with Axios Des Moines

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Twin Cities news?

Get a daily digest of the most important stories affecting your hometown with Axios Twin Cities

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Tampa Bay news?

Get a daily digest of the most important stories affecting your hometown with Axios Tampa Bay

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Want a daily digest of the top Charlotte news?

Get a daily digest of the most important stories affecting your hometown with Axios Charlotte

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Please enter a valid email.

Please enter a valid email.

Subscription failed
Thank you for subscribing!

Achild playing in a fountain on a square to cool himself amid a heatwave in Binzhou, eastern China's Shandong province. Credit: STR/AFP/Getty Images

Heat waves in the North China Plain — China's breadbasket — are predicted to become so severe, they would "limit habitability in the most populous region of the most populous country on Earth," a new study finds.

The big picture: Such heat waves could both threaten lives and dampen economic output in the region, where 400 million people live. Earlier studies along with a separate new analysis released Thursday found the potential emergence of extreme heat waves — from China to West Africa to South Asia — that are far worse than those currently experienced.

Key findings: Like the previous two studies by this MIT team, which focused on the Persian Gulf region and South Asia, the researchers found that given the current pace of greenhouse gas emissions, extreme heat waves are likely to emerge in the agricultural region of the North China Plain between 2070 and 2100. (In the Gulf, the most severe heat is projected to occur over the Gulf waters, rather than land.)

  • The North China Plain is one of the most-threatened areas of the globe due to heat extremes, the study found.
  • The soil there is ideal for agriculture, having been formed from the Yellow, Huai and Hai rivers. Irrigation tends to lower air temperatures, but increase evaporation — with the net effect of making heat waves more intense and intolerable for the human body.
Spatial distribution of extreme wet-bulb temperature in eastern China, including the North China Plain (boxed region), shown with irrigation (IRR) and without. The three images represent historical and future projections based on different greenhouse gas emissions scenarios. Image: Suchil and Eltahir, Nature Communications 2018.

How they did it: Elfatih Eltahir and co-author Suchil Kang of the Singapore-MIT Alliance for Research and Technology focused on wet bulb temperatures — measures of the amount of water vapor in the air that are taken by wrapping a wet cloth around the bulb (or sensor) of a thermometer, to let evaporation of water cool the bulb.

  • At 100% humidity, with no evaporation possible, the wet-bulb temperature equals the actual temperature.
  • The study combines wet bulb temperatures with air temperatures to arrive at a thermal index that corresponds to how the human body responds to heat.
  • The researchers ran a group of regional climate models to simulate changes to this thermal index across the North China Plain region. They looked at the climate during the past 30 years, and used the models that produced the closest matches to reality in order to project future climate in this area.

What it means: As global temperatures increase, the researchers predict heat waves will become far less tolerable as the combination of air temperatures and humidity levels causes the maximum wet bulb temperature to reach or even exceed 35°C, or 95°F.

  • The study identifies this as the level at which the human body cannot survive beyond six straight hours of exposure.
  • This would apply in particular to those working outside, such as farmers and construction workers.
"Climate change could bring a significant risk of deadly heat waves, heat waves that are very severe, heat waves that touch on livability for humans."
— Study coauthor Elfatih Eltahir of MIT

The North China Plain region examined in this study is likely to see a 3 to 4°C, or 5.4 to 7.2°F, increase in wet bulb temperature by 2100 under a business-as-usual emissions scenario, the study found.

  • The risk of such extreme heat would be significantly reduced if greenhouse gas emissions were to be cut, however.
  • China is both the biggest emitter of greenhouse gases in the world, and the most vulnerable to climate change-related heat extremes, the study points out.

Uncertainties: The study's authors tried to reduce the uncertainties associated with regional climate model simulations by using a group of models.

  • It's possible they overestimated the effects of irrigation on heat waves, though observational evidence already supports the emergence of extreme heat waves in this region.
  • According to Michael Mann, director of the Earth System Science Center at Penn State University, "this study too likely underestimates the risk of increased heat waves because it relies upon a modeling framework...that is unlikely to capture the increase in persistent summer weather extremes."

Additional evidence: In a separate report released Thursday, the risk analysis firm Verisk Maplecroft also zeroed in on the wet bulb temperature factor involved in future heat waves.

  • It found that the human body is likely to experience heat stress "in all instances" when performing strenuous exercise when the wet bulb temperature hits 32°C, or 89.6°F.
  • Their analysis found four regions where, absent adaptation efforts, rising heat stress will significantly reduce nations' export values: West Africa, Central Africa, Middle East/North Africa, and Southeast Asia.
  • 10.8% of West Africa's export value will be at risk by 2045, hitting Nigeria and Cote d’Ivoire particularly hard, since so much of this region's exports come from extractive industries that are outdoor labor intensive, per the report.
"But the implications go beyond the boardroom. Reduced product availability and rising production costs will have a ripple effect throughout the global supply chain, meaning consumers will see prices rise."
— Alice Newman, Verisk Maplecroft analyst

Go deeper: 2018's global heat wave is so pervasive it's surprising scientists.

Go deeper

Indianapolis mass shooting suspect legally bought 2 guns, police say

Marion County Forensic Services vehicles are parked at the site of a mass shooting at a FedEx facility in Indianapolis, Indiana, on Friday. Photo: Jeff Dean/AFP via Getty Images

The suspected gunman in this week's mass shooting at a FedEx facility in Indianapolis legally purchased two assault rifles believed to have been used in the attack, police said late Saturday.

Of note: The Indianapolis Metropolitan Police Department's statement that Brandon Scott Hole, 19, bought the rifles last July and September comes a day after the FBI said in a statement to news outlets that a "shotgun was seized" from the suspect in March 2020 after his mother raised concerns about his mental health.

U.S. and China agree to take joint climate action

US Special Presidential Envoy for Climate John Kerry waves as he arrives at the Elysee Presidential Palace on March 10, 2021 in Paris. Photo: Chesnot/Getty Images

Despite an increasingly tense relationship, the U.S. and China agreed Saturday to work together to tackle global climate change, including by "raising ambition" for emissions cuts during the 2020s — a key goal of the Biden administration.

Why it matters: The joint communique released Saturday evening commits the world's two largest emitters of greenhouse gases to work together to keep the most ambitious temperature target contained in the Paris Climate Agreement viable by potentially taking additional emissions cuts prior to 2030.

Biden defends not immediately raising refugee cap

President Biden speaking with reporters after leaving his cart following his first round of golf as president at Wilmington Country Club in Wilmington, Delaware, on Saturday. Photo: Jim Watson/AFP via Getty Images

President Biden on Saturday sought to explain why he didn't immediately lift the Trump administration's historically low refugee cap.

Driving the news: Several Democrats accused Biden Friday of not fulfilling his pledge to raise the limit after it was announced he'd keep the cap. The White House said later it would be raised by May 15. Biden told reporters Saturday, "We're going to increase the number."