What will we tell our kids and grandkids about climate change?

Because when our kids and grandkids ask us what we did about climate change, we need to have a simple, true answer: “Our best.”

A landmark report released Monday by the Intergovernmental Panel on Climate Change predicts that as early as 2030, the Earth will have warmed 1.5 degrees Celsius from pre-industrial levels. According to the report, a world warmed by 1.5 degrees would be less brutal than one warmed by 2 degrees (the goal enshrined in the Paris Agreement), but holding at 1.5 would still require “unprecedented changes” across several sectors, including land use, energy, building, transportation and city planning.

The clock is ticking for humanity. Debra Roberts, co-chair of one of the IPCC working groups, summed up our situation: “The next few years are probably the most important in our history.”

I have twin grandsons, Bailey and Gus, who are almost 3. Their cousin, Teddy, is almost 1. I keep thinking about what I will say when they’re old enough to ask me why we didn’t do more.