Madrid, July 15 (RHC)-- Heatwaves are gripping parts of Europe, China and the United States, where record temperatures expected this weekend are a stark illustration of the dangers of a warming climate.  Extreme heat advisories have been issued for more than 100 million people in the U.S. with the National Weather Service forecasting particularly dangerous conditions in the states of Arizona, California, Nevada and Texas.

Greece’s top tourist attraction, the Acropolis, closed during the hottest hours on Friday as temperatures hit 40C (104F) in the capital, Athens.  Volunteers at the Hellenic Red Cross handed out bottled water to tourists wilting in long lines hoping to beat the closure and scale the steps up to the Parthenon temple.

Authorities have also warned about a greater risk of forest fires, particularly in regions where strong winds are expected.

Italy’s capital, Rome, is expected to see temperatures reach a peak of 43C (109.4F) on Tuesday.  Valerio Mattia of the Italian Red Cross warned that the population is “not aware of the danger that this climatic phenomenon could pose in terms of health.”  The organization has been conducting an awareness campaign on how to respond to heatwaves and runs a hotline to assist those who are socially isolated, Mattia told Al Jazeera.

The mercury may soar as high as 48C (118.4F) on the islands of Sicily and Sardinia, the European Space Agency said, potentially setting “the hottest temperatures ever recorded in Europe.”   Europe’s current record of 48.8C (119.8F) was recorded in Sicily in August 2021.

Elsewhere, parts of eastern Japan are also expected to reach 38C to 39C (100.4F to 102.2F) on Sunday and Monday with Japan’s meteorological agency warning that temperatures could reach previous records.

A major Chinese power company said its power generation for a single day hit a record high this week as parts of China, including Beijing, experienced record temperatures.  But as some baked in the heat, others in China faced extreme downpours. In Chongqing, a sprawling municipality in southwest China, numerous rivers threatened to overflow their banks after unrelenting rains.

The government braced for more extreme weather and issued heightened warnings for heavy rain in 24 districts and counties on Friday, according to state media.

More than 2,600 residents were evacuated early on Friday in Chongqing, the Xinhua news agency reported. State television showed a waterfall of rain enveloping cars and trucks and rivers of thick brown mud burying tractors and lorries on the streets.

North China’s Inner Mongolia region also issued a red alert as intense rainstorms are expected to hit central and eastern parts of the area, according to the region’s meteorological service and water resources authority, Xinhua said.

A contributing factor to the higher temperatures this year may be the climate pattern known as El Nino.  El Nino events, which occur every two to seven years, are marked by warmer-than-average sea surface temperatures in the central and eastern Pacific near the equator and last about nine to 12 months.

Water temperatures off the southern coast of the US state of Florida have surpassed 32C (90F), according to the National Oceanic and Atmospheric Administration.

As for the Mediterranean, surface temperatures will be “exceptionally high” over the coming days and weeks, the World Meteorological Organization said, exceeding 30C (86F) in some parts, several degrees above average.

Warming ocean temperatures can have devastating consequences for aquatic ecosystems both in terms of survival and migration and can also negatively impact the fishing industry.  A new study led by the National Oceanography Centre (NOC) in Southampton, United Kingdom, revealed a change in the colour of at least 56 percent of our oceans over the past 20 years – a surface area that equates to more than all of the land on Earth.

Tropical ocean regions near the equator have become steadily greener over time, the scientists found, indicating that ecosystems within the surface ocean must also be changing to contain the green pigment chlorophyll.