The word 'catastrophe' is bantered about quite a bit when climate change is debated. Deniers try to demean climate science by calling it 'catastrophic anthropogenic global warming' (CAGW). I've also heard people on the science side of the debate discuss various climate change catastrophes. Is either side even realistic? That depends on how you define 'catastrophe.'
Let's first discuss the deniers. They state claims of the end of civilization are crazy. I have to agree with them on this point. If your definition of 'catastrophe' is the end of civilization or even the end of the species (I have heard both claims in recent weeks), I can't accept that future. Let me illustrate why.
Suppose we had an epically catastrophic heat wave. Let's suppose it lasts a full month and kills a million people. I think most people would agree that would be a catastrophe. Just imagine - a million dead bodies piling up in the heat faster than they can be buried. And yet, more than six million babies would be born during that month. In other words, we could have a heat wave greater than anything ever recorded and the human population would still increase.
Understand, I am not in any way predicting such a heat wave. I am merely making a point with a fictional situation. People simply don't understand what it means to say '7.3 billion people' (the current world population). Put it this way. If we reduced the world population by one million people every single day, it would take over 7300 days to wipe out everyone. That's more than 20 years. That's a whole lot of death and I don't see it happening. Not ever. The human species is the most adaptable, more resilient species of life on the planet. Assuming the climate takes a gigantic turn for the worse, I still don't see it wiping us out.
So, does that mean there is no cause for alarm? Again, it depends on your definition of 'catastrophe.' Studies show climate change is already responsible for more than 400,000 deaths per year. That is not some hypothetical number for a future. That is what is happening right now. If you or someone you love is one of those 400,000 per year, you would probably consider it to be a catastrophe.
The fact is, climate change has already resulted in a lower standard of living for hundreds of millions of people. It is already responsible for the deaths and illnesses of millions. It is already responsible for the massive damage to the environment. The list goes on. This is stuff that is already here. What about the future? How much worse will the weather get? How much more will diseases spread? How much more will sea levels rise? How many more droughts and heat waves will there be? Again, the list goes on.
So, will we see catastrophes caused by climate change?
By my definition, it's already here.