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Why this mid-June stretch of hot temperatures in Colorado is different

Posted at 5:19 PM, Jun 14, 2021
and last updated 2021-07-12 16:55:30-04

Temperatures soared to 98 degrees in Denver Monday afternoon - way above the average high of 82 degrees for mid-June, but shy of the record of 102 degrees, set on June 14, 2006.

Colorado is on the eastern edge of a huge bubble of hot, dry air that covers all of the southwestern United States. This hot, dry airmass has little thunderstorm potential, just a few hit or miss storms to bring brief relief from the heat.

Eastern Colorado had some wet weather in recent weeks, so the drought conditions have mostly ended along and east of the Continental Divide, but soils are drying out pretty quickly with this recent hot weather.

Western Colorado, Utah, Nevada, Arizona, New Mexico and California are all experiencing extreme drought conditions. The drought exacerbates the heat wave as the sun’s heat is simply heating up ground as opposed to evaporating water. This compounds the cycle of heat and dryness and is not likely to break for most of the summer.

The hottest weather of the year is typically in mid-July, so this is an early heatwave. With global warming we are seeing hotter weather earlier, so this type of event will become more frequent.

The earliest 100 degree reading on record for Denver is June 11, 2013. The record for June 14 is 102 degrees, set in 2006. We will likely set records Tuesday and Wednesday, as the predictions are 100 degrees both days and the records are at 97 and 96 respectively.

Tuesday's record for June 15 fell, with Denver topping out at 101 degrees.

We reached 100 degrees Tuesday, and if we do so again Wednesday, it would be the earliest ever Denver has had two straight days of triple digits.

June 2012 had 6 days of 100 degrees or hotter, with 2 days reaching 105 degrees – the all-time hottest temperature for Denver. (It has been reached several different days in June, July and August.)

Our hottest weather is typically in July, but we are seeing heatwaves coming earlier in the warm season, while our mid-summer heatwaves are tending to become longer and hotter in recent decades.

The role of climate change cannot be left out of the equation in this weather pattern. As the level of carbon dioxide (CO2) increases in our atmosphere, our world is getting warmer. The effect of increased CO2 in our atmosphere is well understood and has been known for over 150 years.

The climate has always changed, this is true – and, it is exactly why we know what is happening now.

The role of carbon dioxide (CO2) in determining the temperature of our planet is established science, regardless of efforts to discount the impact of CO2.

In 1825, a French mathematician — Joseph Fourier — calculated that given the distance from the Sun, the Earth should be much colder. He theorized that it was the atmosphere that trapped enough heat to make our planet habitable.

In 1856, Eunice Foote, an American researcher, filled glass jars with different gases and set them in the sun. The jar filled with CO2 warmed the most.

In 1863, John Tyndall, an Irish physicist, did more elaborate experiments with carbon dioxide and discovered that CO2 was very effective at trapping long-wave or Earth energy.

In 1895, a Swedish researcher named Svante Arrhenius theorized that a doubling of carbon dioxide in the atmosphere would cause the Earth's average temperature to increase by several degrees. The greatest impact would be in the far northern latitudes – which is exactly what we are seeing!

In the 1970s - CBS anchorman Walter Cronkite, who was famously known as the most trusted man in America, reported on the threat of global warming.

Even though CO2 is a TRACE gas in our atmosphere, it is highly effective at capturing infrared (Earth) energy from escaping into space. The CO2 molecule vibrates a little when infrared energy passes by, this tiny “wiggle” serves to trap that energy in the atmosphere instead of letting it pass through into outer space.

The analogy is to think of each molecule of CO2 like a feather in a down comforter. We are adding feathers at an unprecedented rate, making the blanket of our atmosphere more effective at trapping heat.

On timescales of millions of years, CO2 is mostly a balance between volcanoes that create it and "chemical weathering” (dissolving) of rocks that destroy it. The weathering of rocks creates calcium carbonate that returns the carbon to the soil, the oceans and the Earth’s crust.

When volcanic emissions exceed rock dissolving, CO2 increases and vice versa when volcanic emissions decline.

CO2 was extremely high (maybe 5 times current levels!) 55 million years ago (more volcanoes than dissolving rocks), and it fell steadily for 50 million years straight.

The main reason that CO2 dropped was that India crashed into Asia, raising the Himalayas and Tibetan Plateau. All that fresh rock dissolved fast, sucking down CO2.

When the CO2 got low enough about 2 million years ago (about 300 ppm), we started having ice ages. We have had at least 20 since then.

During ice ages, about ⅓ of all the CO2 dissolves into the oceans, so CO2 drops to around 200 ppm. Then, when the ice melts, it shoots back up to about 300 ppm again. It’s done this 20 times in 2 million years.

During the last great global warming, CO2 rose from 180 to 280 ppm between 18,000 years ago and 8,000 years ago. That’s a rise of 0.01 ppm per century.

Now, as we dig up fossil carbon and light it on fire, the CO2 rises 3 ppm per year, 300 times as fast as it during deglaciation! It is not just the fact that the world is getting warmer, it really is the rate at which the warming is occurring. Since 1800, the CO2 has risen more than it did in 100 centuries after 16,000 BC.

With things changing so quickly, the big concern is how will we deal with the rapid change and whether many species will be able to survive, as there is not time for them to evolve.

How does earth's carbon cycle work? Here is a short explanation that is very good!

Although my job description is mainly to be the “nice, friendly” person that tells folks what the high will be tomorrow and whether the weekend will be nice, for many Americans, the television weather-caster is as close to a scientist as they get, and they invite us into their living rooms!

As TV weather-casters, we are Station Scientists and are often asked to explain related sciences – earthquakes, volcanoes, comets, asteroids, the Aurora Borealis – these are not “weather” – but they are “science."

MORE: Stanford University’s Katharine Maher explains the mechanisms that heat and cool the planet

We should not shrink back from talking about climate change at the risk of losing a viewer. It is our responsibility to provide the public with accurate information about global warming.

People often joke to me that “you can’t even predict tomorrow’s weather, let alone 100 years from now?” I agree that weather forecasting is not always as accurate as desired, but in many ways, climate is much easier to predict than weather.

First of all, it is very important to realize that a heat-wave, tornado outbreak, record flood or major blizzard is not climate — it is weather!

Weather is one play in a football game, climate is the history of the NFL!

Even though an individual severe weather event cannot be blamed on Global Warming, a warmer climate adds energy to the system — "juicing up" the atmosphere and will cause more frequent and extreme severe weather events in the future.

We can expect more intense rain events, such as the Front Range Flood in September 2013, but also more wildfires as the changing climate creates stress on our forests.

Our Colorado climate will become warmer over the next 100 years. Denver will have temperatures more like Albuquerque, New Mexico.

The result will be less snowpack, lower reservoirs and more frequent droughts. We know the population will increase and therefore the demand for water – we need to plan ahead! We have been blessed to have a few big snow years recently, the long-term prospects may not be so rosy.