One of the plain facts about navigation, both in the air and on the open sea, is that a slight course correction, when applied early on, will get you to where you need to be with hardly any extra time or fuel. But the longer you go before recognizing that you need to alter course will take you further from your desired track and will take you more time to get to where you need to be.
The longer you wait to change course, the more costly it becomes.
Which is were we are, now, when it comes to atmospheric CO2 levels. We, as in "humans" have added enough CO2 to the atmosphere to push CO2 levels into unknown territory, at least over the last million years or so:
The change is more apparent when you look at the data over the last millenium:
And the last fifty years:
Humans, as in "we", are conducting a global climate experiment of "what happens if we inject several millions of tons of carbon into the atmosphere every year for several decades?"
The world is getting hotter. What happens is that the global ice caps melt. Glaciers are receding around the world. The ice sheet over Greenland is melting faster than the mathematical models predicted it would. The sea level rise projections made a few years ago, that the seas may rise a meter or so, are going to be very optimistic. Sea levels may rise on the order of meters, from both the addition of ice melt and thermal expansion.
Additionally, as the globe warms, other not-so-fun things happen. The American wheat belt will likely become unsuitable for that crop. Those areas experiencing hot days (100 degrees or higher) in the summer, which through the 1980s were largely limited to the desert southwest, will spread further and further north. Tropical diseases will follow the heat.
Plants and animals will migrate with their comfort zones, but only to a limited amount. The temperature rise is shaping up to be drastic enough that it is unlikely that evolution can occur in time for species to adapt. To be blunt about it, we are looking at a version of
the K-T event. Additional atmospheric CO2 means that the pH of the seas change, which will mean bad things for coal, shellfish and who knows what else, making the seas a component of humanity's global experiment.
As far as local effects go, a warming globe means that winter precipitation may come more as rain than as snow. That may sound good to you, since rain doesn't need to be plowed, but that also means a smaller snowpack (or none at all) in the mountains. For locations that obtain a lot of their fresh water from the melting of the winter snowpack, such as Los Angeles, that spells disaster. In regions of the world where several nations draw their fresh water from rivers that have their origins in mountain that are now capped by glaciers and snowpacks, the argument over who gets what water may lead to war. (I suspect that the modernization of the Chinese military is, in part, driven by this.)
What can be done about it? At this point, probably not a damned thing. We have passed the point where minor alterations of the economy would have staved off what is happening and what will happen. Inertia, greed, ignorance, whatever, all of them and more meant that we did nothing when we could have. Even if humanity was able to dial back its carbon output to 1960, there are over twice as many humans now as there were then.
What will happen is that the world will change, probably more drastically than we can imagine. Our descendants will forget that we fought off fascism and that communism collapsed. They will forget that terrorism was a threat. They will not remember the International Space Station or the Moon landings. But they will remember that there was a period when humanity's use of carbon as fuel could have been addressed in time to stave off climate change and that humanity chose to do nothing.
They will curse our memory, probably for as long as civilization survives.
Enjoy your weekend.
(H/T for the carbon graphs)
