Heatwaves, wildfires mark summer of extremes

WMO – Intense heat has gripped large parts of the Northern Hemisphere in this summer of extremes, causing major damage to people’s health and the environment, said the World Meteorological Organization (WMO). China set a new national daily temperature record, and many new station temperature records have been broken.

Wildfires have caused devastation and dozens of casualties and forced evacuations of thousands of people in parts of the Mediterranean, including Algeria, Greece, Italy and Spain. The Copernicus Atmosphere Monitoring Service (CAMS) recorded a significant increase in intensity and emissions from wildfires in the eastern Mediterranean during the second half of July, particularly in Greece. The emissions from these wildfires have been the highest for this period of time in Greece in the last 21 years. Canada has seen its worst wildfire season on record, harming air quality for millions of people in North America.

Sea surface temperatures have hit new records, with severe marine heatwaves in the Mediterranean and off the coast of Florida.

“The extreme weather – an increasingly frequent occurrence in our warming climate – is having a major impact on human health, ecosystems, economies, agriculture, energy and water supplies. This underlines the increasing urgency of cutting greenhouse gas emissions as quickly and as deeply as possible,” said WMO Secretary-General Petteri Taalas.

“In addition, we have to step up efforts to help society adapt to what is unfortunately becoming the new normal. The WMO community is providing forecasts and warnings to protect lives and livelihoods as we strive to achieve our goal of Early Warnings for All,” Taalas added.

A rapid study from climate scientists in the World Weather Attribution network said that the heatwaves bore the clear footprint of climate change.

“Without human induced climate change these heat events would however have been extremely rare. In China, it would have been about a one-in-250-year event while maximum heat like in July 2023 would have been virtually impossible to occur in the United States/Mexico region and Southern Europe if humans had not warmed the planet by burning fossil fuels,” said the attribution study published on July 25.

Heatwaves are amongst the deadliest natural hazards with thousands of people dying from heat-related causes each year. The full impact of a heatwave is often not known until weeks or months afterward, WMO experts said.

France, Greece, Italy, Spain, Algeria and Tunisia reported new maximum daytime and overnight station temperature records.

Figueres (Catalonia), reported a new temperature record of 45.4 degrees Celsius on July 18 and a station on Sardinia recorded 48.2 C on July 24.

In Algeria and Tunisia, the highest maximum temperature was respectively 48.7 C (Dar El Beïda/Argel) and 49.0 C (Tunis and Kairouan) on July 23.

In some parts of the Mediterranean, a further continuation of the extreme heat into August is possible, said the WMO’s Regional Climate Centre for Europe.

“An increasing number of studies demonstrate connections between rapid warming and the Arctic and mid-latitude weather patterns, including in atmospheric dynamics such as the jet stream. The jet stream becomes weaker and wavier when warm air is transported to the north and cold air to the south. In these conditions, near-stationary weather patterns establish and lead to prolonged heatwaves and drought in some regions and heavy precipitation in others,” said Alvaro Silva of the WMO climate services division.

Turpan in China’s Xinjiang province, had a temperature of 52.2 C on July 16, a new national temperature record according to the China Meteorological Administration.

Large parts of the United States also were gripped by extensive heatwaves, with high temperatures in numerous places, according to the National Weather Service (NWS), which said a few locations could register their all-time temperature records.

The NWS issued repeated excessive heat warnings and advisories, often covering more than 100 million people. In the latest update issued on July 31, it warned the dangerous heat in the affected areas would continue through Aug. 5.

In the south-central and southeast U.S., maximum heat index values could near or exceed 43 C. Many parts of Florida, including the city of Miami, have been hit by an extended, record-breaking heatwave.

As of July 30, Phoenix, Ariz. recorded 31 days of daytime temperatures above 43.3 C and overnight low temperatures of more than 32.2 C.

“We need to broaden focus beyond maximum temperatures because the minimum temperature is most important for health and critical infrastructure,” said WMO extreme heat senior advisor John Nairn.

A temperature sensor at Furnace Creek in Death Valley National Park in California recorded 53.3 C on July 16, according to the WMO.

According to the WMO Archive of Weather and Climate Extremes, the hottest temperature recorded was 56.7 C on July 10, 1913.

Wildfires forced the evacuation of hundreds of residents and tourists on the Greek islands of Rhodes, Evia and Corfu since July 17. The emissions of these wildfires have reached record levels, with an estimated total of one megaton of carbon emissions between July 1 and 25, almost doubling the July 2007 record, following several days of high intensity fires, according to Copernicus Atmospheric Monitoring Service.

In Algeria, there were several dozen reported casualties.

Hot, dry conditions have fueled an early an intense wildfire season in Canada. The fires have forced more than 120,000 people to evacuate their homes and polluted the air for millions more across North America.

Record-breaking wildfires continue to burn big forest areas in Canada, with more than 650 wildfires were out of control as of July 24. Also, more than 11 million hectares were already burnt in 2023 – compared to the 10-year average of about 800,000 hectares, said the Canadian Interagency Forest Fire Centre.

The record levels of emissions generated by the intense wildfire activity across Canada in May and June had a major impact on air quality, both in Canada and further afield. According to CAMS data, fire radiative power (FRP) for the country as a whole in the first three weeks of June was significantly higher than the 2003 to 2022 mean, with estimated carbon emissions at over 100 megatonnes for the month. Emissions levels from the start of the year until the first week of May remained close to the 2003 to 2022 mean, but then quickly rose to significantly higher than any previous year in the CAMS record.

The fires continued to rage at the end of July, with numerous fires breaking out within Canada’s Arctic circle.

Sea surface temperatures (SSTs) of the Mediterranean Sea are exceptionally high over the coming days and weeks, exceeding 30 C in some parts, and more than 4 C above average in a large part of the western Mediterranean.

Unconfirmed reports said that Manatee Bay, Florida, recorded a sea surface temperature of 38.4 C – warmer than a hot bath.

The impacts of marine heatwaves impacts include migration of species and extinctions, arrival of invasive species with consequences for fisheries and aquaculture.

Heavy rains and flooding caused severe damage and loss of life in several parts of the world.

Forty people were reported killed as torrential rain and flash floods hit South Korea on July 14 and floods in northwest China killed a reported 15 people, prompting President Xi Jinping to urge greater efforts to protect the public from extreme weather.

In northern India, roads and bridges collapsed and houses were swept away as rivers overflowed during heavy monsoonal rainfall and flooding which killed dozens of people. The mountainous state of Himachal Pradesh was badly hit, as were the regions of Punjab, Rajastan and Uttar Pradesh. New Delhi reportedly marked its wettest July day in 40 years, with 153 millimetres of rain falling in one day.

The Japanese Meteorological Agency (JMA) issued heavy rain emergency warnings on July 31 for the Fukuoka and Oita prefectures. A new daily rainfall record of 376.0 mm fell on July 10 at Minousan and 361.5 mm at Hikosan, both in the Kyushu region.

In the northeastern U.S., parts of New England faced yet more torrential rainfall on saturated soils following serious floods at the start of July. New York issued a flash flood emergency, and more than four million people were under flood alerts on July 11.

“As the planet warms, the expectation is that we will see more and more intense, more frequent, more severe rainfall events, leading also to more severe flooding,” said Stefan Uhlenbrook, the WMO’s Director of Hydrology, Water and Cryosphere.