Because of climate change, heat waves and extreme heat are becoming more often and intense. That frequently conjures up pictures of people seeking cover from the blazing heat or of city kids cooling off in a fountain as their parents perspire nearby.
Even while climate change is increasing the heat of our days, its effects are more obvious at night than they are during the day. The fact that evenings are warming up more quickly than days is alarming because warm nights prevent our bodies and minds from cooling off, which has negative health effects.
Here is what we know about how temperatures differ at night compared to during the day and why it matters.
WHAT WAS NOTICED Nearly 30 years ago, scientists examined if and how daytime and nighttime temperatures had changed between 1951 and 1990 using information from more than 2,000 meteorological stations around the globe. They discovered that, on average, both minimum (nighttime) and maximum (daytime) temperatures had risen throughout the stations they examined. However, the minimum temperature had increased by 1.4°F while the maximum had increased by 0.5°F. In other words, throughout that period, nights warmed more than days. The difference between the maximum and minimum temperatures within a day, often known as the diurnal temperature range, was significantly reduced by those modifications.
many studies have confirmed the globally averaged pattern of stronger nighttime warming than daytime warming since that study was conducted three decades ago, and we now have a better understanding of the size of the shift since 1901. We now know that there are variations in nighttime vs. daytime warming vary across the globe and that this trend does not apply everywhere. While other regions, like Australia, don’t show any discernible patterns, some, like North America, demonstrate unambiguous and consistent signals that nighttime warming is greater than daylight warming.
According to the Fourth US National Climate Assessment , the average minimum and maximum temperatures across the United States are 1.4F and 1.1F warmer than they were in the first half of the 20th century, respectively.
WHY DO EVENINGS WARM MORE RAPIDLY THAN DAYS? In a nutshell, clouds are the solution.
Because a warmer atmosphere can theoretically contain more moisture, global warming is making land areas cloudier. During the day, the thick, precipitating clouds cloud type specifically reflects sunlight back into space and cools the environment. However, at night, they behave as a blanket, absorbing heat and then re-emitting it back down to Earth’s surface. Climate change is acting like the blanket you don’t need in a stuffy room on a hot summer night by increasing cloud cover.
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Because of everything mentioned, evenings warm up more quickly than days.
A recent study shown that nighttime warming is exceeding daylight warming in regions of the world where cloud cover, humidity, and precipitation have increased. The contrary is also true: Daytime warming is exceeding nocturnal warming in regions of the world where cloud cover, humidity, and precipitation have decreased. These patterns can also be influenced by other elements, such as the moisture content of the soil.
HOW MUCH MORE OFTEN, GIVEN CLIMATE CHANGE, ARE HOT NIGHTS? A tool created by our pals at Climate Central demonstrates how much climate change is affecting US temperatures on a daily basis. Most days, it is clear how much greater the effects of climate change on nocturnal temperatures than daylight temperatures.
Climate Centrals Climate Shift Index (CSI) analyzes the prediction for today’s high and low temperatures (as well as the projections for the upcoming several days) and determines whether climate change is increasing or decreasing the likelihood that those temperatures will occur. A climate change index of zero indicates that the predicted temperature is essentially unchanged from what would occur in the absence of climate change. A anticipated temperature that is one to five times more likely due to climate change is indicated by an index value of one to five.
Since the tool’s release, I’ve checked the CSI maps every day, and they consistently demonstrate that climate change is having a bigger influence on low temperatures at night than on high temperatures during the day.
For instance, on July 8, 2022, we can see that climate change is increasing the possibility of the predicted high temperatures in places like Texas and Colorado by 1-2 times, as indicated by the yellow and orange colors:
However, if we look at the day’s forecast for the midnight low temperature, we can see that throughout broad areas of the southern half of the country—the darkest red color on this map—climate change is making extreme temperatures as much as five times more likely:
Studies have also revealed that the diurnal temperature range fluctuates between seasons and that winters tend to be warming quicker than summers, therefore it will be interesting to see if that holds true throughout seasons other than summer.
WHY IS IT IMPORTANT? People now anticipate that during a heat wave, lower nighttime temperatures will offer relief from the sweltering days. Anyone who has spent time in intense heat can attest to how our bodies can begin to cool off at night after a scorching day. However, when nights are warm, health hazards and scientists 0 scientists 1 arise because our systems are unable to expel the additional heat that has built up over the day. Imagine a person laboring in agriculture or construction all day long in temperatures above 100 degrees. They are more likely to suffer from scientists 2, heat-related illnesses, injuries, and death if they cannot find relief at night because nighttime temperatures are also high.
High temperatures alone strain our bodies, but they also significantly impair our ability to produce scientists 3, which has its own set of negative effects on cognitive function, attention, memory, etc. When it’s hot, scientists 4 and individuals in low-income nations are more vulnerable to sleep loss.
The scientists 5 can make hot nights even worse in metropolitan settings. Due to their abundance of heat-retardant materials and surfaces, such as asphalt, cement, and pavement, cities typically experience higher temperatures than their surroundings on any given day. The excess heat that cities collect during the day is then radiated back into the atmosphere at night, keeping the air there up to 22F warmer than the rest of the country.
scientists 6 also adds to the heat in the urban environment at night. The urban heat island effect can be scientists 7 when there are heat waves because it shortens or removes the time when it is cooler and people can rest their bodies and minds.
For people without access to air conditioning or for whom the decision to turn on the air conditioning presents challenging financial trade-offs, the health risks associated with hot nights are particularly severe. People with scientists 8 and scientists 9 are more at risk since they tend to reside in hotter metropolitan areas or have less financial flexibility to maintain the air conditioning. These situations are frequently the outcome of long-term underinvestment in the health and wellbeing of people of color and the places in which they live as a result of decades or centuries of systematic racism. Millions of people may be affected when they are unable to cool off at home at night due to heat-related power outages or preemptive power cuts made to reduce the risk of wildfires.
AVOIDING MORE DANGEROUSLY HOT NIGHTS IN THE FUTURE As heat-trapping emissions rise, climate models predict that the frequency of high daytime and nighttime temperatures will both rise in the future. However, the many studies 0 is divided on whether the diurnal temperature range would rise or fall over the United States. In high-emissions scenarios, the average nighttime temperature across the US will rise by about 9F (5C) by the end of the century, which is comparable to the many studies 1 that the country is anticipated to suffer in that scenario.
However, many studies 2 that depends on the emission choices we make in the ensuing decades and how well we are able to restrict future warming to 1.5C or 2C, as well as the frequency and severity of events that involve both hot days and hot nights. In fact, within a few years of achieving net-zero global emissions, it is predicted that global temperatures would hit many studies 3.
Our nights could be more peaceful and secure if we reduced our emissions immediately and drastically. Every year, heatwaves and hot nights in the US claim hundreds of lives, therefore we must also be putting in place the proper measures to assist people stay safe and healthy even on hot nights. For example, city planners and public health departments must continue addressing the issue of urban heat islands; grid operators and utilities must continue to push for greater reliability while also making a concerted shift to clean energy sources; and states should adopt many studies 4, which forbids utilities from cutting off a person’s electricity even if they are behind on their bills during a heat wave.
It’s commonly believed that many studies 5 of deaths are heat-related. We must take action if we want to truly prevent them in the face of warmer days and warmer nights.
By many studies 7, courtesy of many studies 6
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