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What Permanently Passing the 400 ppm Atmospheric CO2 Threshold Means

By: Daniela Garcia

Here at San Diego Surfrider we know that local beaches and oceans are treasured by the San Diego community, so we work hard to make sure they can still be enjoyed for years to come. But when you look on more of a global scale, maintaining the cleanliness of our oceans becomes extremely complicated once we realize the detrimental effects of greenhouse gases on oceanic health. But how are these two related? Let’s take a deeper look:

When the Industrial revolution began in the 1700s in Britain, it quickly spread to other parts of the world. Soon after that, many countries were inventing machines that were used in factories that ran on dirty coal, which released enormous amounts of greenhouse gases into our atmosphere. We now know that greenhouse gases are the cause of man­made climate change, and our climate has been continually warming since the release of gases like CO2 and methane in mass quantities.

In order to track the amount of CO2 in our atmosphere over the years, the Keeling Curve was created in 1958 by Charles David Keeling, a professor of the Scripps Institution of Oceanography in San Diego, CA. Measurements of CO2 parts per million (ppm) concentrations are taken at the Mauna Loa Observatory in Hawaii and are placed on a graph to show the annual fluctuations. Below is the Keeling Curve, with the last CO2 reading of December 12, 2016.

Let’s put this in perspective. Before the Industrial Revolution, global atmospheric carbon dioxide levels were around 280 ppm. The highest amount of global CO2 in our atmosphere that is considered a “safe” amount is 350 ppm. But for the entire duration of the month of March, our global CO2 levels reached 400 ppm.

The lowest amount of CO2 in our atmosphere occurs during the month of September each year, because is after the summertime months when plants are done growing and done sucking up all the CO2 they possibly can. As the year progresses, the leaves of these plants fall off and start decomposing, which releases the CO2 they have stored in their leaves back into our atmosphere.

This past September, when atmospheric CO2 should have been at it lowest, the monthly value never dropped below 400 ppm. This means that we have permanently crossed this threshold, which has been considered the climate ‘tipping point’ of no return.

According to a blog post by Ralph Keeling, the scientist who is in charge of the carbon dioxide monitoring program at the Scripps Institute of Oceanography, “The monthly [ppm] value for October will therefore almost certainly also stay above 400 ppm and probably will be higher than 401 ppm. By November, we will be marching up the rising half of the cycle, pushing towards new highs and perhaps even breaking the 410 ppm barrier”. Thankfully, looking at the latest reading of atmospheric CO2 at Mauna Loa Observatory, the current amount if 404.48ppm, but the relief doesn’t last. Atmospheric CO2 rose 3ppm in the last 2 months.

This means that globally, we have not taken the actions we need to combat the disastrous effects of climate change like losses in biodiversity, coastal flooding, and ocean acidification. It also means that 2016 is on the trajectory of being the hottest year we have on record. It shows that we need to intensify our efforts to educate the public and pass legislation that prevents companies and countries from continuing their unsustainable energy habits. And within the past year, there have definitely been tremendous efforts by 21 countries to reduce their carbon emissions, while simultaneously growing their GDP,  which shows that is is possible to be environmentally sustainable while also becoming increasingly economically stable.

There are also plenty of ways you can change your own habits in order to be environmentally friendly and reduce your CO2 emissions! The STOP Coastal Climate Change committee with San Diego Surfrider is completely dedicated to educating the public on what you can do to reduce your impacts on climate change. One way to start is by consuming less energy, as electricity and heat production are the biggest contributors to global greenhouse gas emissions. You can do this by investing in sustainable companies, refusing to use single-use products, turning off your lights when they don’t need to be on, or investing in insulating products for your home so that the need to use AC/heaters won’t be as necessary. For more ideas and information on other forms of reducing your carbon emissions, take a look here.


If you would like to become actively involved with the STOP Coastal Climate Change committee, please join the Facebook page. This is where event pages are posted for our monthly meetings, which are typically held on the second Wednesday of each month.  We hope to see you there!