I was wondering the same a couple of weeks ago, dave. A GP was among those arrested and he said, quite sincerely, that humans are now experiencing "Hell on Earth" due to climate change. He said "many millions" of people had already died because of it and that this is only the beginning.
I'm a little worried for the sanity of people like him (and to be honest, he should be doing a bit more GP-ing and a little less gluing himself to roads or walking slowly backwards down the Cromwell Road). People have always died because of weather events, particularly in places likely to see heavy rainfall or high temperatures. Bangladesh in particular springs to mind. For so long as I can recall, that country has suffered floods. It endures annual monsoon rainfall and many of the people living in the south - an area dominated by large deltas - are flooded out regularly.
No doubt any floods that have occurred in recent years are said to have been caused by climate change. In fact they are caused by monsoon rain falling on an area totally unsuitable for human habitation.