There is plenty of hyperbole surrounding climate change, so let's get this out of the way first. No, the Earth is not going to be destroyed because of global warming. The Earth is far more resilient than that. Even humanity will almost certainly survive, unless the resulting resource wars somehow manage to trigger global thermonuclear war.
But just because the worst things we can imagine won't happen it doesn't mean that more realistic scenarios aren't horrible enough.
Let's start with sea level rise. In the latest IPCC report, possible sea level rises until the year 2100 range from 26 cm for the most optimistic scenario to 98 cm for the most pessimistic, depending on how CO2 concentrations will develop in the coming decades - and, as the report notes, sea level rise is likely to continue after 2100.
Now, for obvious historical reasons, much of Earth's most valuable real estate is within a short distance of the coast. Many of the world's greatest cities are ports - New York City, Tokyo, Singapore, Mumbai, and many, many others. What would happen if sea levels were to rise half a meter? Remember, that's only the average sea level - storm surges will also reach higher.
Either they will have to surround the cities with Dutch-style dikes - which is enormously expensive - , or they will have to abandon the areas closest to the coast and rebuild everything deeper inland, including the entire infrastructure - which is also enormously expensive. And, of course, smaller towns or poorer countries will not be able to shoulder such expensive, which means that they will have to go for the second option.
Then there will be all those climatic shifts. "Global Warming" will not be a uniform process. Some places will get a lot warmer, while others barely so. Some places will get much more precipitation, and some much less.
And all our local agriculture and infrastructure is optimized for our current local climate. The rich nations of the world will be able to cope... probably. We can adjust our farming techniques and update our infrastructure so that we can still produce crop yields - and if that fails, we will probably still have enough money to buy our food from elsewhere. But the poorer nations won't have the means to adapt and change, which means that their inhabitants will attempt to leave en masse. And we will notice a few hundreds of millions of refugees on our doorsteps.
Beyond agriculture, there is the shift of ecosystems. Numerous species suddenly can't live in their usual habitats any more, because the temperature and the precipitation changed. The oceans are getting more and more acidic thanks to all the dissolved carbon dioxide, with unknown effects on the most fundamental components of the oceans' ecosystems. We do not yet know how that will affect our food sources, but it would be foolish to assume it doesn't. And beyond that, this mass extinction represents a truly epic loss of genetic diversity - of information. What might we have learned about biology, genetics, and numerous other subjects by studying these species? What inventions might have been inspired by this information?
We will never know.
And worse, much of this is probably inevitable. Already, the permafrost in the Arctic is thawing, releasing massive amounts of methane which will likely continue the warming process even if humanity were to somehow stop emitting CO2 tomorrow. It's a very slow process, taking place over decades and even centuries - but it is quite likely unstoppable.
"So what's the use?" you might ask. "If all this is inevitable, shouldn't we just give up on reigning our CO2 emissions in?"
Well, we might not be able to stop global warming any more, but we can still affect the rate at which it occurs. Reducing our emissions will slow it down, which buys us time. Time to adapt, for both us and the species that live around us. Time to figure out new technological solutions to combat both the warming and its effects.
Even beyond the likely loss of human lives, global warming represents a huge economic drain on the world's funds. And worse it gets, and the faster it arrives, the bigger this drain will be. By causing this change, we are forcing our descendants to spend much of their resources on mitigating its effects, rather than improving themselves and their lives - or even just enjoying their lives. And, of course, if current life extension research works out, we will be damaging our own prosperity as well.
We can argue all day how we are supposed to reduce our CO2 emissions - but that is a topic for future blog posts. However, in my mind there is no doubt about the need to reduce them.
