klimato

There is no participle in this word. Esperanto's passive present participle is -at-, and a learner who has just drilled amata and farata will see klim-at-o and try to read it as the thing being klimmed. There is no root klim-, the -at- is not an affix here, and klimato is a single indivisible borrowing. The affix instinct is the right instinct and it will earn its keep across thousands of words; it just needs the habit of checking the root list, because when it misfires it misfires confidently.

Keep it apart from vetero. The weather is what is happening outside today; the climate is the pattern over years. Esperanto draws the line exactly where English does, which is convenient, and the confusion in both languages is the same confusion. Klimata ŝanĝiĝo is climate change, and klimata krizo is the crisis, both fully standard.

The Greek behind it is a small pleasure. Klima meant a slope, the tilt of the earth's surface towards the sun, and ancient geographers divided the world into zones by that angle. So when you say the climate of a region, you are still, four languages later, talking about how steeply it leans. The figurative sense came along too, and la politika klimato works in Esperanto exactly as it does in English.