For that matter, solar x-rays and extremely low frequency radio waves are both part of sunlight, but play little role in climatology.
"we lack a single word for the study of this thing. Doesn’t this seem odd?"
Ummm, no? "Plant biologist", "organic chemist". Many scientific fields use more than one word to describe them. Some people even use "water scientist" or something similar, instead of "hydrologist". Here are a few:
"Jay Famiglietti is Senior Water Cycle Scientist" -- https://science.jpl.nasa.gov/people/Famiglietti/
"In addition, a full time Water Scientist position has been created to assist Council in the management of the project" -- http://www.gloucester.nsw.gov.au/environment/water-study-pro...
"Mount Rainier Jr. Water Scientist Report" - http://www.nature.nps.gov/geology/gip/web_products/MORA_2010...
It's silly for the aliens to be hung up on word boundaries. Teach them German or another language which permits words like Stromtarifrechner ("electric bill calculator") for what in English requires three words.
As to the topic at hand, the problem isn't due to a change in incoming sunlight, it's due to an increase in greenhouse gases in the atmosphere, which decrease planetary cooling. This is part of climatology, which is one word. Or "earth system science" (three words) or systems ecology (two words).
> when the body comes under attack, we run a temperature. .... “Planetary temperatures are common when a species, typically a young one, upsets the balance. In some cases the new species integrates quickly and restores balance. In other cases the temperature creates challenges that reduce its population, and sometimes the species is wiped out completely. It’s very similar to the process in the human body.”
That's a strawalien. Elevated body temperatures as a response to infection appears to be an evolutionarily acquired trait, though we aren't sure if it has a direct benefit or is a side-effect of some other response. It's not similar to a planetary ecology, which is decidedly non-Darwianian.
In no cases did the species integrate quickly to the new balance? In no case did the new species trigger decreased temperatures, of the Snowball Earth kind? With all their experience in the great galaxy, I find it hard to believe they only came across one type of ecosystem perturbation.