Monthly average atmospheric carbon dioxide levels have topped 410 ppm for the first time in more than 800,000 years, according to recent research.

There's good reason to think this will have disastrous effects on human health.

CO2 levels will dramatically increase pollution levels and related diseases, cause extreme weather events including deadly heat waves, and broaden the ranges of disease-carrying creatures like mosquitoes and ticks.



The concentration of carbon dioxide in Earth's atmosphere hasn't been as high as it is now since long before humans existed. Just recently, CO2 levels topped 410 ppm, according to according to observations made at the Mauna Loa Observatory in Hawaii.

There's good reason to think this will have catastrophic effects on human health.

Carbon dioxide levels don't necessarily have direct effects on our ability to breathe (at least, at these concentrations). But by transforming the planet, these CO2 levels will still dramatically increase pollution and related diseases, potentially slow human cognition, cause extreme weather events (including deadly heat waves), and broaden the ranges of disease-carrying creatures like mosquitoes and ticks.

Right now, CO2 levels are still climbing rapidly. They could be on track to hit 550 ppm by the end of the century, which would cause average global temperatures to rise by 6 degrees Celsius. (The goals of the Paris Agreement are to try to limit warming to less than 2 degrees C, which would help limit the severity of some of these effects — we'd still see some, but it's considered to be the best we can do.)

REUTERS/Oswaldo Rivas

Heat waves

Searing temperatures are already the deadliest form of extreme weather. Heat waves kill tens of thousands of people and are responsible for more deaths in the US every year than the combined effects of hurricanes, lightning, tornadoes, earthquakes, and floods.

A study published last year in the journal Nature Climate Change found that 30% of the world is already exposed to heat intense enough to kill people for 20 or more days each year. That level of intensity is defined using a heat index that takes into account temperature and humidity; above 104 degrees Farenheit (40 degrees C ), organs swell and cells start to break down.

In 2010, more than 10,000 people did in a Moscow heat wave. In 2003, some estimates say a European summer heat wave killed up to 70,000.

CO2 concentrations in the atmosphere drive temperatures up. If they aren't brought under control and continue unchecked (we're currently on track for at least a 3 degree C rise), some experts think that 21 out of every 100,000 deaths in the US will be caused by heat.

Pollution

Higher levels of CO2 also exacerbate ozone and other pollution levels. A recent study found that air pollution kills 9 million people every year. As temperature rises, that'll get worse.

One 2008 study found that for every degree Celsius the temperature rises because of CO2 levels, ozone pollution can be expected to kill an additional 22,000 people via respiratory illness, asthma, and emphysema.

At the same time, non-ozone air pollution linked to warmer weather will increase rates of lung cancer, allergies and asthma, and cardiovascular disease.

Disease-causing ticks are spreading in warmer weather. Getty Images

A plague of ticks and mosquitoes

As the world gets warmer, ticks, mosquitoes, and other disease vectors are expanding their habitats and are able to spread disease for longer before cold weather shuts them down for a season.

We're already seeing this happen, as a recent CDC report revealed — diseases like Lyme disease, Dengue, and Zika spread by these pests tripled in the US between 2004 and 2016.

We don't have good ways to control mosquito populations and we're terrible at stopping ticks. As a result, these conditions, known as vector-borne diseases, are expected to become bigger problems as CO2 cranks up the global thermostat.

The floods from storms like Hurricane Harvey could be even worse in the future. REUTERS/Richard Carson

Hurricanes and fires

And of course, the larger-scale planetary changes caused by accumulating atmospheric CO2 are also expected to affect human health. As CO2 warms the planet, ice sheets are melting and seas are expanding, making cities more vulnerable to storms.

Higher temperatures are expected to lead to more intense storms with more rainfall, and as the past year demonstrated, that can have a huge effect on people. Last summer, the Caribbean and US Gulf Coast were hit by devastatingly strong hurricanes, one of which dumped an unprecedented amount of rain on Houston. Flooding caused by heavy monsoons in South Asia killed 1,200 people.

Wildfires are also getting worse as CO2 concentrations increase — something experts link to warmer temperatures. Thousands of buildings were razed by record-breaking wildfires in California last year. The amount of land burned in the US since 1984 is double what would have been expected without the effects of climate change in that period, according to one study. And the average wildfire season in the west now lasts at least two and a half months longerthan it did in the early 1970s, according to WXshift, a project of Climate Central.

Time is running out

When President Barack Obama's EPA ruled in 2009 that CO2 was a pollutant that needed to be regulated under the Clean Air Act, they listed health effects like these as a reason to consider CO2 concentrations dangerous. The Trump administration's is reevaluating that ruling, but these facts are still listed on an archived Environmental Protection Agency page.

We're already seeing many of these effects today. Without a rapid transition away from fossil fuels, most experts believe these consequences will become more and more severe. Cutting back on CO2 isn't enough to stop these effects — at this point, we need to cut them down to zero and ideally figure out ways to remove some CO2 from the atmosphere in the first place.

These are good reasons to do so.