I would like to encourage M Houlding to volunteer in the sub-arctic Hudson Bay, with Earthwatch, a science-based not-for-profit group that has been researching climate change for more than 40 years.
If so, he would learn the following from the research:
A) Permafrost is gradually melting; this releases high levels of methane into the atmosphere that is many times worse than carbon dioxide in contributing to global warming, thus exacerbating the temperature rise.
B) The boreal tree-line is moving northwards, altering the ecology.
C) Polar bear numbers are diminishing due to: Firstly, den sites collapsing with the warmer temperatures.
If, after copulation, the female bear does not find a den, the embryo does not implant and the pregnancy is lost. Secondly, the sea is freezing later in the season, meaning later access for the polar bears to their hunting grounds for their diet of seal meat.
Thirdly, the bears have to travel further to reach their quarry.
Due to their resulting poor condition, fewer bears survive the harsh environment each year, and the number of cubs per pregnancy has also declined markedly.
The Greens, including Dr McLean, base their views on the state of the planet on science-based information.
M Houlding would be sensible to do likewise.

M Ware, Otumoetai.