Across the state of Nevada, people are starting to feel the effects of the climate crisis.
Most noticeably, they’re feeling the heat.
Now, the desert Southwest of the United States has always been pretty hot – there’s no denying. But the last several years – and this year, in particular – have served as a warning of the truly dangerous heat to come if we don’t slash fossil fuel emissions.
In June, Las Vegas had to set up shelters and temporary cooling stations after excessive heat warnings were issued by the National Weather Service. By August, the state had broken a record for most consecutive days over 105 degrees. Later that same month, Las Vegas Valley tied a record high for the date at 110 degrees. Las Vegas itself may be the fastest-warming city in America.
Nevada has warmed about 2.8 degrees Fahrenheit on average across the state since 1970. Throughout the state but especially across its south, long-lasting heat waves are becoming more common. And that’s just to start.
Snow in the mountains of Nevada and key nearby states is melting earlier in spring, and with precipitation patterns become more and more erratic, water flow in the Colorado and other rivers in Nevada is likely to decrease. This low river flow creates a snowball effect that will weaken the productivity of ranches and farms and increase the frequency and intensity of wildfires.
What’s happening in Nevada is the same thing happening all around the world. Rising temperatures are fundamentally altering the water cycle and shifting precipitation patterns. In many areas, rain has become either increasingly abundant or in desperately short supply, relative to longtime averages. And at the same time, warming is causing snow to melt earlier in spring, and more and more water is evaporating from bodies of water, soils, and more.
The result, in many places: Dwindling lakes, rivers, and reservoirs, and parched land.
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Importantly for Nevadans, the climate crisis has put a strain on two very important bodies of water: the Colorado River and Lake Mead.
The water in Lake Mead, the vast reservoir on Nevada’s border with Arizona, sits at just 39 percent of what the lake can hold. That has a lot to do with the diminishing river that feeds it – the Colorado River, which more than 40 million Americans depend on for drinking water, irrigation, and much more.
To fully grasp the impact our changing climate might have on a river, you should start at its literal source. Much of the water flowing down the Colorado River originates as snow high up in the Rocky Mountains.
But the high-elevation snowmelt that constitutes the headwaters of the Colorado is shrinking. Spring seasons are arriving earlier and earlier, and with highly variable annual precipitation, mountain snows simply cannot keep up with the rising demand for water downstream, including in vast swaths of southern Nevada.
“As the climate warms, less precipitation falls as snow, and more snow melts during the winter. That decreases snowpack — the amount of snow that accumulates over the winter. Since the 1950s, snowpack has declined in Nevada, as well as in the other states in the Colorado River Basin,” EPA explains.
Much of southern Nevada is already desert, and annual average rainfall statewide is far more likely to decrease than increase, adding to the threat of drought and desertification in this region.
Around the country, the number of days each year when the heat index will exceed 100 degrees is expected to more than double, according to a 2019 study by the Union of Concerned Scientists. (The heat index is what it actually feels like outside and is a combination of both temperature and relative humidity.)
To put this number into context, the National Weather Service describes a heat index of 91 as the starting point for extreme caution for heat disorder (especially for those who at risk through prolonged exposure or strenuous outdoor activity). At a heat index of 104 and above, we get into the zone marked “Danger.”
For much of Nevada, particularly the southern part of the state, these numbers are cause for serious concern. (It’s important to remember here that northern and southern Nevada often experience quite different temperatures.) On average, the overall state of Nevada has historically seen around 12 days per year with a heat index above 90 degrees. If current emissions continue, that number could climb to 39 days per year by midcentury and 68 by 2100, the study predicts.
Stop for a minute to think about what these numbers actually mean. By the middle of this century, kids across Nevada could be in borderline dangerous territory for heat stroke and other illnesses just by playing outside. For more than a month each year.
And the region around Las Vegas will have it worse. Already substantially hotter than the central and northern parts of the state, southern Nevada now experiences around 99 days per year where the heat index reaches more than 90 degrees. By century’s end, the area could easily see as many as 150 days per year that cross this (very) red line.
As for days with a heat index above 100 degrees, the average could reach as high as 96 per year by 2100.
All on its own, heat is the most dangerous weather phenomena we know, causing more deaths annually than tornadoes, floods, or hurricanes in the US.
Why? Extreme heat elevates the risk of dehydration and heat stroke, and can affect people’s cardiovascular, respiratory, and nervous systems.
Heat doesn’t threaten everyone equally. The elderly and very young, as well as people with chronic illnesses, lower-income communities, and people who work outdoors, are particularly vulnerable to extreme heat-related health effects. These include an elevated risk of death from conditions like heart attack, organ failure, and more.
Even more troubling, higher temperatures are made worse in cities and other urban settings where the large buildings, pavement, and other surfaces retain the daytime warmth, something known as the “urban heat island effect.”
Cities can be on average several degrees warmer than their leafy or wide-open rural counterparts – and Las Vegas is one of the worst urban heat islands in the US. At plus-7.3 degrees Fahrenheit, Vegas ranked as the city with the most intense summer urban heat island effect (that is, average daily urban-rural temperature difference) over a 10-year period ending in 2014, according to a Climate Central study.
The danger goes beyond just heat. Rising temperatures like these, particularly in highly concentrated urban areas, also increase the formation of ground-level ozone, the main ingredient in city smog. Exposure to high levels of ozone can lead to shortness of breath, wheezing and coughing, chest pain, and temporary decreases in lung function. Exposure even increases the risk of premature death from heart or lung disease.
Wildfire Risk is Growing
As we’re seeing right now in parts of the American West, particularly Nevada’s neighbor, California, the climate crisis helps create the conditions for dangerous, fast-moving wildfires.
Why? Well, let’s start with that premature spring snowmelt and runoff we mentioned earlier.
With many places seeing their snowpack melt up to four weeks earlier than just 50 years ago – and at the same time, as unseasonably warm temperatures creep deeper into the fall – forests, which are considered combustible about a month after the snowmelt ends, are now vulnerable to fire for a much longer period of time than they used to be.
At the same time, warmer and drier conditions also make forests more susceptible to pests. Drought reduces the ability of trees to defend themselves against attacks from many pests, including, importantly for Nevada and the US Southwest, bark beetles.
Bark beetles infested 28,000 acres of Nevada’s forests in 2014. And longer-lasting warm weather and milder winters extend the life and breeding cycles of many pests like these, allowing some to persist year-round, and opening the door for new pests and diseases to become established and thrive.
These three things – dry conditions, longer fire seasons, and pest infestations – create favorable conditions for forest fires to quickly get out of hand.
Pretty soon, all that parched land and dead, dried-out plant life becomes tinder, igniting when the heat soars and lightning strikes or high winds down an active power line or a careless cigarette butt is tossed in the wrong direction.
Add into the mix more development in the wildland-urban interface (aka, the areas between established built-up communities and undeveloped nature), and you have an increasing number of structures and people being placed at risk too.
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This combination of hotter, drier conditions, more fires, and drought could change the Nevada’s landscape as we know and love it today.
So how do we fight back?
By taking action.
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