Two political cartoon collections. Search by topic => 700+ climate cartoons
Several associations/websites devoted to political cartoons are searchable by topic.
In the Cartoonist Group website, keyword search for "climate" pops up nearly 450 entries, in very small thumbnails, including the caption in larger (readable) font alongside. Copyright protection blocks copy/pasting.
Searching for "climate" in The American Association of Editorial Cartoons (AAEC) site, yields 30-80 small thumbnails for each recent year. Captions are unreadable, unfortunately.
Each site has its own rules regarding use and copyright
The Cartoonist Group
American Association of Editorial Cartoonists