The Guardian (23 July) has a report on the Ken Sprague Fund competition based around the theme of global warming. 19 of the winners and runners-up can be found in a related gallery, including the winning entry by Russian cartoonist Mikhail Zlatovsky (above).
I don't know if this was part of the same competition—I've a feeling it may have been—but I saved the following cartoon recently... funny and scary at the same time.
Another picture saved recently is even more scary because it's not a cartoon but a photo. If I remember correctly, it's a church in Spain which once sat on the edge of lake that has now completely dried up. There's just something haunting about it...
(* Apologies... I've no idea who has the copyright on these.)