(Image source: Keeling Curve)
Back in early March we began to warn that CO2 levels could break 400 PPM in 2013. In April, the Mauna Loa Observatory recorded hourly CO2 levels above 400 PPM for the first time in more than 4 million years. Then, two days ago, daily averages for 400 PPM CO2 were breached.
Whether May averages just below or slightly above 400 PPM CO2 remains to be seen. But it is certainly possible that weekly and even monthly averages of CO2 break this severely high threshold this year. Almost certainly, a month or two of 2014 will see CO2 averages over 400 PPM. By 2015 or 2016, yearly averages for CO2 will exceed that extraordinarily dangerous level.
This massive jump to 400 PPM CO2 from pre-industrial averages is disturbing and alarming for many reasons. The first of which is the heating impact CO2 has on the Earth’s atmosphere. According to Paleoclimate data, a world at 400 PPM CO2 is, on average, between 3 and 4 degrees Celsius hotter. Even worse, temperatures in the Arctic average about 14 degrees Fahrenheit hotter. This increase in temperatures results in radical alterations to the world’s climate, pushes major sea level rises, and results in massive volumes of ice melted. It is doubtful that most of the world’s glaciers and ice sheets could survive such a long-term assault of extreme high temperatures. And it is worth noting that human beings as we know them have never occupied a world without ice.
But even as bad as maintaining CO2 levels at 400 parts per million may sound, worse are the potential feedbacks such a high initial spike of atmospheric carbon may kick off. Vast stores of methane lay locked in the world’s tundra and oceans. Even a small fraction of these gasses liberated by human-caused warming would serve to add more greenhouse gasses to the atmosphere, further increasing the warming already in store. In addition, as the ice sheets recede, more dark ocean and land features are exposed to sunlight. This loss of albedo results in increased solar heat absorption, further increasing global temperatures. So past climate may not be a perfect analogue to what we may be setting in place. Instead, it may be the launching point for even worse changes.
At 400 parts per million there is the danger that such terrible consequences may well become permanent features of the world in the coming decades and centuries. The current danger is somewhat low due to the fact that, if we were to rapidly reduce emissions now, we might be able to secure a livable climate and let the Earth’s natural processes reduce CO2 levels to 350 PPM or lower over the course of about a century. However, there is risk that the current human forcing is enough, even now, to generate a powerful response from the Earth’s climate and environment. One strong enough to result in CO2 levels stabilizing at the current level or even increasing somewhat due to these natural feedbacks. In order for this to happen, global climate would have to be much more sensitive than scientists currently estimate. But the fact is that, at current CO2 levels, such a dangerous feedback is possible, if not likely.
What is even more maddening, though, is the fact that human CO2 emissions and global CO2 levels are rising at a break-neck pace. Just last year, May CO2 levels peaked at an average of 396.8 PPM. This year’s levels are likely to be 3 PPM+ higher than last year. Global averages have been rising at a rate of 2.2 PPM per year or more. So at the current rate of CO2 rise and factoring in the rate of increased CO2 emissions, it is likely that 450 PPM could be breached in about 20 years. This pace of increase is faster than at any time visible in the geological past by at least a factor of 5. In short, it is likely that Earth has never undergone such a radically rapid increase of CO2.
At 450 PPM CO2, the world is far more likely to experience the kind of powerful global feedbacks noted above. And with world CO2 emissions continuing to increase, it is fair to say that we are in the era of this dangerous climate change now. Which it is why it is very important to recognize that with each passing year of CO2 emission increases and failure to reduce overall world carbon emissions, we pass deeper and deeper into an extraordinarily dangerous territory. Pushes to reduce atmospheric CO2 levels to the ‘safe range’ of 350 PPM must be pursued with great speed and effort if we are to preserve hope of a livable climate for human beings beyond the first half of this century.