We were told at school that atmospheric carbon dioxide was 0.03%. We now tell the kids that it's at 0.04% and rising still, perhaps with a one-year blip last year, who knows. We know that we have caused that to happen. The rise in the last 150 years is a perfect match for the temperature rises in both hemispheres on land and at the sea surface, measured over tens of thousands of readings. Can't prove the connection, as we don't set out to prove things in that way in science, but the correlation is shudderingly close, and science does test and take note of correlations in an attempt to explain what is causing what. We know that polar ice and mountain glaciers are melting fast. We know that sea levels are rising fast. We understand the greenhouse effect. When it comes to becoming convinced that climate change on the current scale is unlike any previous event and is having deleterious effects on life on the planet, well there will never be a single big event to clinch it. Events such as wildfires in Australia and California, droughts in sub-Saharan Africa, the dire threat to polar bear habitat, more intense and frequent storms and killer heatwaves are all just tiny pieces of a massive jigsaw, the more pieces you find, the more the bigger picture makes sense. Unfortunately, we are unlikely to be around to fit the final few pieces. And of course it was cold at the weekend and we had snow in Cornwall two weeks ago so don't give me all that global warming crap.