Deadly heat waves are hitting cities on four northern hemisphere continents, a sign that climate change may once again spark temperatures that exceed last summer’s, which was the hottest in 2,000 years, according to research published in the journal Nature .

Record temperatures of recent days are believed to have caused hundreds, if not thousands, of deaths in Asia and Europe.

In Saudi Arabia nearly 2 million Muslims went to worship at its Grand Mosque Meccabut hundreds died due to extreme temperatures that exceeded 51° Celsius, according to reports from foreign authorities.

Health and security sources in Egypt told Reuters on Thursday that at least 530 Egyptians had died on the hajj, an increase from the 307 reported on Wednesday, while 40 were still missing.

The countries that are wet by the Mediterranean are being hit for another week by high temperatures that may have contributed to wildfires in various regions — from Portugal to Greece and along the northern coast of Africa to Algeria — according to the National Oceanic and Atmospheric Administration of USA (NOAA).

In Serbia forecasters are predicting temperatures to hover around 40°C this week as winds from North Africa create a warm front in the Balkans. Health authorities declared a red alert and advised citizens to avoid leaving their homes.

Belgrade’s emergency service pointed out that its doctors had to intervene 109 times during the night to help people with chronic health problems.

In the neighbor Montenegro, where authorities have also urged citizens to stay in shady places until the late afternoon, tens of thousands of tourists seek some coolness on beaches along the Adriatic.

And the east coast of the usa are for the fourth consecutive day under a warm dome, a phenomenon seen when a strong high pressure system traps warm air over an area, preventing cold air from passing through and keeping temperatures high.

In New York City, cool spaces were created in libraries, senior employment centers and other infrastructure. Schools in the city are operating as normal, but in several areas in the surrounding suburbs, classes ended earlier than normal to allow students to escape the heat.

Meteorological authorities issued yesterday, Thursday, an extreme heat warning in some areas of Arizona, including Phoenix, where the temperature is expected to reach 45.5° Celsius.

In its neighboring state New Mexico Two wildfires have killed two people, burned more than 93,000 acres and destroyed 500 homes, authorities said. The heavy rains that have been occurring may help fight the fires, but storms that broke out yesterday caused flash flooding, complicating firefighting efforts.

A total of nearly 100 million Americans live in areas for which extreme heat warnings were issued yesterday.

High temperatures are expected to begin to subside in the northeastern US starting today, the weather service said, but in New York and the southernmost states the heat will persist through the weekend.

Counting the dead

The summer season in India lasts from March to May, when with the onset of the monsoons the temperature starts to drop.

But on Wednesday, New Delhi recorded its highest temperature in at least 55 years, with the Safdarjung observatory recording a temperature of 35.2°C at 1am.

Normally, temperatures drop during the night, but scientists point out that due to climate change, night temperatures are also increasing. In many areas of the world, nighttime temperatures are rising faster than daytime temperatures, according to a 2020 study by the University of Exeter.

New Delhi has completed 38 consecutive days with the maximum temperature reaching or exceeding 40° Celsius.

An Indian health ministry official said on Wednesday that there were more than 40,000 suspected cases of heatstroke and at least 110 confirmed deaths between March 1 and June 18, when northwestern and eastern India saw twice as many hot days as usual.

Record temperatures

The heatwaves follow 12 consecutive months of being the hottest on record, according to the EU’s climate change watchdog.

The World Meteorological Organization says there is an 86% chance that one of the next five years will be warmer than 2023.

Although the average global temperature has risen by about 1.3°C since pre-industrial times, climate change is causing even higher temperatures, making heat waves more frequent, more intense and longer lasting.

A global average heat wave that would have occurred once every 10 years in the pre-industrial era will now occur 2.8 times every 10 years and be 1.2°C warmer, according to the World Weather Attribution International Science Group ( WWA).

Scientists estimate that heatwaves will continue to intensify if the world continues to emit greenhouse gases by burning fossil fuels.

If global temperatures rise by 2°C compared to pre-industrial times, heatwaves will occur an average of 5.6 times per 10 years and be 2.6°C warmer, the WWA noted.