Whoever deleted this answer did the right thing.
It is an incoherent piece that primarily displays prejudice and racism. It does that through a short string of allusions rather than bringing forth anything that would resemble a stringent argument.
Basically it says something like that: "dark people are dumb" and that "city dwellers are dangerous".
For 'referencing' that, there are then two links thrown in that have not much to do with the assertions presented.
One link leads to an abstract of a short study that talks somehow "about IQ" (and claims to find a correlation with that and suicide and homicide), but it is from a dubious person basing his 'research' on again racist 'political scientist' (Charles Murray).
More importantly, the report linked to knows nothing about climate at all. The most central claim at the start of the answer is therefore not referenced or "sourced". That is abusing a source trying to simulate referencing. Since the 'reference' is unrelated to the claim, this is cargo cult referencing.
Since OP here on meta quite rightly doesn't really find what is claimed either, the ensuing desire to comment for clarification is almost obvious:
wish to comment on the answer to ask for references for 'IQ as climate indicator' and also to ask why USA, Australia, Spain have high urbanization rates but low violence.
It seems strange when OP then goes on to insist on
"It is sourced."
It is obviously not. The answer is a short collection of unsustainable generalisations that are not referenced, that in fact can't be referenced with reliable sources that are not racist,
The point to observe is the main reason for deletion: that it's raving mad racism with abuse of name-dropping of scientific concepts almost completely unrelated to the content, with cargo cult referencing, and a lack of arguments and absence of stringency. Even OP here wants to comment in ways that should make it clear that eg "IQ as climate marker" is absolute nonsense (or is that the reason for US civil war outcome? ;). A non-answer.
For the benefit of OP asking for the possible influence of climate on cognitive performance, a wholly different take than in the deleted answer would be Environment and intelligence. The most cardinal sin of abusing "IQ" as a shorthand for 'intelligence' – another generally untenable position – one might take a read over from Taleb: IQ is largely a pseudoscientific swindle - INCERTO - Medium.
Since it looks like quite a few 'answers' to this question wanted to get 'this point' across, that there would be 'different countries with different IQ-levels':
That is complete bogus. An IQ-test is designed and calibrated to put individuals on a ranking system that actually reflects them being a member of the target population. All proper IQ-tests are calibrated to form a normal distribution with the average being always exactly 100! So taking an American IQ test and administering it to the most perfect English speaking Indians fails the basic validity criterion: by measuring something in people that are not part of the target population the test was designed for and calibrated on. Thereby, by giving you an average from mass testing that is ≠100, proving nothing more than that the test used was not culture-fair and improperly calibrated. Any conclusions drawn from such a gross mismeasurement are worthless.
Even more egregious is the silently to be assumed range of the explanation of "low-IQ = higher crime". That is so far from depicting reality adequately as to be just untrue:
The American Psychological Association's 1995 report Intelligence: Knowns and Unknowns stated that the correlation between IQ and crime was -0.2.
This implies that the explained variance for this variable 'IQ' is less than 4% for these negative outcomes in 'crime'. (Example for a large Danish sample on juvenile offenses)