Earth just hit a terrifying milestone for the first time in more than 800,000 years -- and it could be bad news for cities

VCG/VCG via Getty ImagesSevere flooding in Shanghai, China.
  • In April, for the first time in recorded history, the average monthly level of CO2 in the atmosphere exceeded 410 parts per million (ppm).
  • This trend could lead to tens of thousands of pollution-related deaths and makes natural disasters, like hurricanes, more powerful and frequent.
  • Cities tend to have higher levels of carbon-dioxide – due to a phenomena known as “CO2 domes” – than non-urban areas, putting city residents at risk for adverse health effects.

Humans have been able to track CO2 levels as far back as 8,000 years ago. From these observations, we know that the atmosphere and the air we breathe has never had as much carbon dioxide in it as it does today.

Scientists have known that for a long time, but according to a new finding from Mauna Loa Observatory in Hawaii, CO2 levels have reached a point that could have catastrophic effects on human health.

As BI’s Kevin Loria reported on Tuesday, for the first time in recorded history, the average monthly level of CO2 in the atmosphere exceeded 410 parts per million (ppm) in April. Research suggests this trend could lead to tens of thousands of pollution-related deaths, slow human cognition, and result in more frequent and powerful natural disasters.

While this new record is dangerous for the planet overall, it could be even worse for urban areas, where more than half of the world’s population lives.

Some researchers believe that high levels of CO2 can form as “domes” over cities. According to a study from Stanford University, CO2 domes can have a drastic local impact, because they worsen the effects of localised air pollutants that cause respiratory diseases. The study’s lead author, Mark Jacobson, estimates that the effect is already causing 300 to 1,000 deaths in American cities each year. That figure is likely higher for cities in developing countries.

Most of the scientific community agrees that there’s a relationship between climate change, rising CO2 levels, and natural phenomena like heat waves, sea-level rise, and superstorms. As the world sees a rise in CO2 levels, coastal cities – from New York City to Shanghai – become even more at risk of flooding from storm surges.

These findings highlight the need for a regional approach to reducing greenhouse-gas emissions, especially within urban areas.

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