Nighttime temperatures are increasing faster than daytime temperatures, with significant impacts on the climate and the environment.
It is a pattern that scientists and climate experts have observed in the recent years throughout the planet, with a possible relationship with extreme weather events, such as the heat wave that is affecting the northwestern United States and part of Canada.
This occurs because the increase in minimum temperatures , usually those that occur during hours when there is no sun, are accelerating compared to maximum temperatures , usually daytime.
That is, warmer nights. This is in contrast to the idea that nights are generally cooler.
This is what some scientists call “heating asymmetry” , and It happens because the effect of the increase in temperatures is not uniform throughout the planet all the time.
With record maximum temperatures, the focus of attention this year has focused on the North American heat dome , a “just one in 1 event. years ”and“ virtually impossible ”if it were not for the effect of human action on the environment, According to the World Weather Attribution network said.
But not everything is about measuring how much the maximum temperatures rise. Scientists are keeping an eye on variations in minimum temperatures, a detail that would be crucial to understanding climate change.
Highs and Lows
Last June has been, since records are kept, the hottest June in the US and Canada, with hundreds of deaths and affected by extreme heat.
The heat intensified between the end of June and the beginning of July in the form of a heat dome, which raised temperatures in both countries like never before .
In British Columbia, Canada, a all-time high of 49, 6ºC , more than four points for above the national record d e 46 ºC.
In Portland, Oregon, a state known for its rainy weather, record highs were also recorded for three days in a row: 46 , 1ºC, 44, 4ºC and 42 ºC respectively. Wildfires in this state have almost burned 150 thousand hectares, causing thousands of evacuations.
But although the maximum temperatures surprised (and worried) the experts, in the range of minimum temperatures there were also changes.
According to data from the National Office of Oceanographic and Atmospheric Administration, only in the last week of June the maximum temperature records were broken about 1. 328 times throughout the US
This figure is due to the daily measurements recorded by each one of the measurement stations deployed throughout that country.
But in contrast, with regard to minimum temperatures, the maximum records were broken some 1.602 times.
“There is a global trend that nighttime temperatures increase at a faster rate than daytime temperatures ”, say scientists from the Institute of Sustainability and Environment at the University of Exeter in England.
It was the same as had warned the Special Climate Science Report in 2017 by ensuring that the average minimum temperatures were increasing “at a rate slightly higher than the average maximum temperatures”, a pattern that was being observed in different parts of the planet.
In fact, unusually warmer minimum temperatures are becoming increasingly common in the US, according to more data from NOAA.
Why do temperatures rise at night?
Daniel Cox, from the Inst ituto of Sustainability and Environment, explains why night temperatures change at a different rate than daytime temperatures.
He and a team of scientists studied the maximum and minimum temperatures per day and hour between 1983 Y 2017 from the data provided by NOAA.
“The exploration of the variation in temperatures has focused mainly on the daily, monthly or annual averages. . Surprisingly little attention has been paid to the variation in rates throughout the daily cycle ”, reads the study, published in the journal Global Change Biology.
After analyzing the data, the scientists found that 54% of the earth’s surface had experienced an asymmetry of warming greater than 0, 25 ºC between day and night.
“The increases in CO2 in the atmosphere and other greenhouse gases are increasing the maximum and minimum temperatures with a greater tendency at night. But the addresses in which these changes occur varies depending on the place and time of day. ”
Not only that. They also found that a greater increase in nighttime temperatures was related to humidity and cloud generation.
“We found that in those regions where there was an increase in clouds, the nighttime temperature increased faster than the daytime one . While an increase in daytime temperatures was related to drier regions “, explains Cox.
This occurs because the clouds act like” a blanket “, pushing heat down and trapping it on the surface land. The more heat on the surface, the more water vapor in the air, which in turn traps more heat.
In cloudless areas, on the other hand, the climate becomes drier and hotter during the days , but the temperature decreases at night as the heat is “released”.
Is this related to extreme weather events such as heat waves?
For Cox, heat waves as extreme as those seen in North America are very specific events that must be studied with more detail, while he and his team analyzed the data for 35 years.
However, Cox says that his study is a first approximation and that many questions remain to be answered to understand how even the small changes that occur on the planet have great implications.
“As increase the levels of eff gases ect greenhouse in the atmosphere, extreme events will become more and more common. But temperatures do not increase linearly. ”
Higher temperatures at night may have direct implications on the environment, such as photosynthesis and plant respiration, according to Cox.
But it will also have negative effects on people. Higher nighttime temperatures mean that the earth does not have enough time to cool go away . This also means that our bodies cannot cool down, especially during extreme heat peaks.
If the body does not acclimate to temperature, dizziness, nausea, fainting and sweating may occur. And in extreme cases, heat stroke can occur, requiring medical help.
Understand the climate change
The planet has warmed approximately 1.2ºC since the industrial age began. Y 2020 has been the second hottest year in history since records have been recorded, surpassed only by 2016.
To continue with the warming projections, as they increase temperatures, the planet could exceed the threshold of 1.5ºC between 2030 Y 2052 , according to the Intergovernmental Group of Experts on Climate Change (IPCC).
Scientists have been trying to predict how climate change may affect the planet.
But events as extreme as the heat dome and the unexpected floods in Germany and Belgium are making experts think that projections are falling short and that the consequences of climate change are making themselves felt earlier than expected.
However, Cox believes that there is a positive side in all this and that analyzing the variations of temperatures by hours can be useful.
“By considering climate change temporarily during the daily cycle, we can more accurately assess climate change and the threat what it represents, ”he says.
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