Earth just hit a terrifying milestone for the first time in more than 800,000 years

Humans like us — Homo sapiens — only evolved about 200,000 years ago, but ice-core records reveal intricate details of our planet's history from long before humans existed. By drilling more than 3 kilometres deep into the ice sheets over Greenland and Antarctica, scientists can see how temperature and atmospheric carbon dioxide levels have changed from then until now. From that record, we know the atmosphere and the air that we breathe has never had as much carbon dioxide in it as it does today.
For the first time in recorded history, the average monthly level of CO2 in the atmosphere exceeded 410 parts per million (ppm) in the month of April, according to observations made at the Mauna Loa Observatory in Hawaii.
The new record is not a coincidence — humans have rapidly transformed the air we breathe by pumping CO2 into it over the past two centuries. In recent years, we've pushed those gas levels into uncharted territory.
That change has inevitable and scary consequences. Research indicates that unchecked, this trend could directly lead to tens of thousands of pollution-related deaths, reach a point at which it slows human cognition, and lead to the rising sea levels, searing heat waves, and superstorms that scientists project as effects of climate change.
"As a scientist, what concerns me the most is what this continued rise actually means: that we are continuing full speed ahead with an unprecedented experiment with our planet, the only home we have," climate scientist Katharine Hayhoe said on Twitter about the new record.
For the 800,000 years we have records of, average global CO2 levels fluctuated between about 170 ppm and 280 ppm. Once humans started to burn fossil fuels in the industrial era, things changed rapidly.
Only in the industrial era has the number risen above 300 ppm. The concentration first crept above 400 ppm in 2013, and continues to climb.
Scientists debate the last time CO2 levels were this high. It might have happened during the Pliocene era, between 2 and 4.6 million years ago, when sea levels were at least 18 to 24 metres higher than today. It may have been in the Miocene, 10 to 14 million years ago, when seas were more than 30m higher than now.
In our 800,000-year record, it took about 1,000 years for CO2 levels to increase by 35 ppm. We're currently averaging an increase of more than 2 ppm per year, meaning that we could hit an average of 500 ppm within the next 45 years, if not sooner.
Humans have never had to breathe air like this. And it does not seem to be good for us.
Global temperature tracks very closely to atmospheric levels of CO2. The potential impacts of higher average temperatures include tens of thousands of deaths from heat waves, increased air pollution that leads to lung cancer and cardiovascular disease, higher rates of allergies and asthma, more extreme weather events, and the spread of diseases carried by ticks and mosquitoes — an effect we're already seeing.
Source: Business Insider