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What it means to live in a world with CO2 concentrations above 400 ppm

The planet has passed the 400 ppm threshold, permanently. It has already happened before, but we could never see a month with CO2 concentrations below the safe level of 350 ppm.

Bad news comes from the Scripps Institute for Oceanography of San Diego, California. Atmospheric carbon dioxide has passed the 400 ppm (parts per million) threshold, maybe permanently.

In September carbon dioxide in the atmosphere is usually at its minimum, but in 2016 it failed to drop below 400 parts per million. “Is it possible that October 2016 will yield a lower monthly value than September and dip below 400 ppm? Almost impossible,” writes Ralph Keeling, the scientist who runs the Scripps Institute for Oceanography’s CO2 monitoring program. “Over the past two decades, there were four years (2002, 2008, 2009, and 2012) in which the monthly value for October was lower than September. But in those years, the decrease from September to October was at most 0.45 ppm — which would not seem to be enough to push October values below 400 ppm this year”.

400 ppm
CO2 levels in January 2015

400 ppm, permanently

It’s not the first time that the atmosphere concentrations of carbon dioxide pass the 400 ppm threshold. It happened in Manua Loa, Hawaii, in 2013 and 2015. But this year’s figures are likely to be permanent.

Gavin Schmidt, NASA climate scientist, has confirmed the trend: “At best (in that scenario), one might expect a balance in the near term and so CO2 levels probably wouldn’t change much — but would start to fall off in a decade or so. In my opinion, we won’t ever see a month below 400 ppm”.


What it means to live with CO2 levels above 400 ppm and why it’s scary

Many studies and researches on climate are based on borings in Arctic ice. This allows discovering how CO2 levels have changed throughout eras and, thus, creating climate models and forecasting future scenarios.

Tens of scientific studies have shown that such CO2 levels were registered 15 to 20 millions of years ago, when the Earth’s climatic conditions were significantly different as far as climate, geography and species are concerned. Plus, humans haven’t made their appearance yet.

What worries the most is that those levels had been reached over thousands of years. Instead, the 400 ppm threshold has been passed over nearly 150 years.

In 2015 we entered a new era of climate reality

The World Meteorological Organization (WMO) has confirmed that CO2 has passed a historic threshold of 400 ppm for the first time in 2015. “The year 2015 ushered in a new era of optimism and climate action with the Paris climate change agreement,” said WMO Secretary-General Petteri Taalas. “But it will also make history as marking a new era of climate change reality with record high greenhouse gas concentrations. The El Niño event has disappeared. Climate change has not”.

Why figures are worrying

Figures are clear and have been confirmed by different scientific institutes. And the World Meteorological Organization has released them in view of COP22, which will take place in Morocco from 7 to 18 November 2016.

“Carbon dioxide (CO2) accounted for about 65% of radiative forcing by long-lived greenhouse gases,” reads a note of the WMO.  “The pre-industrial level of about 278 ppm represented a balance between the atmosphere, the oceans and the biosphere. Human activities such as the burning of fossil fuels has altered the natural balance and in 2015, globally averaged levels were 144 per cent of pre-industrial levels”.

CO2 is not the only responsible though. Methane (CH4) is the second greenhouse gas that has long-term effects, accounting for 17 per cent of radiative forcing. 60 per cent of this amount comes from human-related activities such as cattle, agriculture and biomass burning.

Scientists agree on one thing: CO2 concentration won’t return below the threshold in the next few decades, if not more.

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