A few years ago, we had a drainlayer in to deal with our boggy Auckland garden. Cheerful guy. He commented that in the previous few years, rain like he’d never seen had been causing problems on properties that had, like ours, been fine until now. Then he teased me when I said something about climate change.

As a climate change commissioner, James Renwick has made it his business to talk across disconnects like this. To help people make the leap. He does so in Under the Weather by giving us a vivid, expert lesson in not just climate but weather, the stuff people can see, understand, recognise as reality. Then he explains how it’s going to change.

We’re in for a “complete makeover”, he writes, and he’s very good at explaining what that will be like. Banana farms in Northland. Pineapples. Fire. Hardly any frosts, anywhere.

Severe droughts. Melting roads; warping railway tracks. New pests and fungal diseases. Lots and lots more rain—and the sorts of punishing storms that stay parked up for days. There’s an excellent section where he flips sea-level rise onto a horizontal axis: that is, he explains how far inland the sea will chew when it rises by, say, 50 centimetres. (He calls sea walls and stop banks “wishful thinking”, and advises that we start planning for managed retreat now.)

Moments of memoir leaven the science. Renwick writes about flying a balsa-wood toy plane in a 172 kilometre-per-hour Canterbury nor’wester, and hooning after it on his bike as it disappeared into the distance. Staring out his window in Kāpiti, watching snow fall and knowing that in a warming climate it would likely be a once-in-a-lifetime experience. The sadness that hits him every time he looks at homes built low along coastlines.

In places he’s extremely bleak. But if anyone starts making different choices after reading this book, it won’t be because he guilted them into it. Systems change is the goal here, not nudging consumer choices. A dairy farmer could read cover to cover and not feel picked on. Quite a feat, in a book about climate, and I suspect it’s no accident. You’ve got to bring the people with you.

Only once does this measured man get angry. “We need to dethrone big oil,” Renwick writes, and you can sense he typed that bit extra hard. “They buried the scientific reports produced by their own scientists and started a campaign of disinformation and deceit that continues to this day… Money is the driver. Of course it is… The only cost that matters to them is monetary; environmental and humanitarian costs simply do not register.”

With similar zeal, he argues that as climate change bites, we have a moral obligation to support the people of the Pacific. “Most importantly, we can—and I believe we must—support any displaced communities that need to find a new home in New Zealand.”

As for systems change? He has a wish list. Vastly improved, sustainable public transport. The normalisation of active transport like cycling and walking, and knitting the infrastructure for it into our cities. Car-sharing schemes. More electric cars and more chargers to serve them. More solar and wind farms. Insulation. Efficient home appliances. Retiring every coal boiler in the country. And being climate-strategic about urban development and how we use land.

Renwick has a feeling that once we start to see emissions trending down, there will be a tipping point, such as in all the most terrifying climate models—except this will be a sliver of hope begetting change begetting hope. And his final sell is a powerful one. Imagine, he writes, “a world where climate change isn’t happening”.