At the outset, let me tell you some theoretical human health impacts from ongoing climate warming in the mean are just that - theoretical. I was brought to this topic by an article I received from what I consider an advocacy group which might not be as objective as I’d prefer. I sought out what I feel is a more objective organization with a deeper foundation of scientific expertise and research underlying its hypotheses, evidence, and actual peer-reviewed conclusions. The U.S. National Institutes of Health/NIH has within it the National Institute of Environmental Health Sciences/NIEHS.
There are some impacts from warming which are all but inevitable, and have been known for some time. Vectorborne diseases are going to spread and increase into some new habitats.
Malaria is the No. 1 killer in the world, though U.N. World Health Organization intervention has reduced mortality in recent years in sub-Saharan Africa. Two malaria-carrying mosquito vectors have been found near the U.S.-Mexico border, farther north than during recent decades. The U.S. has also been free of yellow fever and dengue fever for a long time. But we are vulnerable to their vectors migrating farther north as well. This is not to suggest we will suffer epidemics of these tropical diseases. But an increase in temperatures and moisture can also increase the vector population and make migration farther north more likely. (However, in more frequently drought-stricken regions, populations may lessen for certain vectors.)
NIEHS is balanced in its look at potential changes in the epidemiology of cancer. It notes more likely and frequent flooding events (such as on the Mississippi) could increase human exposure to known industrial carcinogens through both direct contact and through volatilization of those compounds into the air, and might increase certain types of cancer. https://us.123rf.com/450wm/panicattack/panicattack1408/panicattack140800005/30652226-green-toxic-chemical-waste-flowing.jpg?ver=6
Increased exposure to UV radiation through reduced ozone in the stratosphere would lead to more skin cancer. But they also point out, less UV would increase production of Vitamin D in humans, and more Vitamin D may possibly play a preventative role with some other type of cancers, though the evidence on the latter is not nearly as well established as the link between UV and skin cancers, including melanoma.
Cardiovascular disease and stroke: NIEHS points to the increased occurrences of both heart attacks and stroke in extreme cold and extreme heat. While extreme cold will likely become less common, more extreme heat is already upon the planet, and increasing. Peer reviewed analysis shows the European heat wave of 2003 was associated with 70,000 premature deaths. A shorter Chicago heat wave in 1995 is linked with 739 premature deaths in 5 days. Yes, we had terrible heat waves in the past, such as in some years during the 1930s. But we are irrefutably experiencing more heat waves globally in recent decades. We are also seeing more elevated ozone pollution events at the surface in warm-weather months (i.e. local air pollution advisories and warnings). High ozone levels near the ground harms pulmonary gas exchange and causes heart stress.
More frequent occurrence of heat stress on crops will reduce yields, especially in poorer, developing nations. Many types of crop pests will have increased populations, leading to more use of insecticides and herbicides. There can be an increase in what’s called the aflatoxin mold for people who subsist more on corn and nuts. Aflatoxin is closely tied to liver disease.
Ocean acidification, which is rapidly increasing due to the oceans’ absorption of the extra carbon from the higher concentration of CO2, can lead to “more virulent strains of existing pathogens and changes in their distribution or emergence of new pathogens.” Moreover, rising sea level temperatures can result in an increase in certain bacteria, including those which cause cholera.
The added CO2 is favorable to growth conditions for quite a number of plants, including some valuable crops. But that also includes more pollen in the air from weed, grasses and trees for longer periods, making allergy seasons longer and tougher. NIEHS also states higher CO2 means greater “allergenicity” for pollen and mold spores; that means more potent, if you get their drift.
I’m only able to scratch the surface here, since I’m writing an article and not a book. Not everything about warming will be a negative; for example, certain food crops do better in a warmer climate. But lest anyone be tempted to cherry-pick the literature and evidence for the “good stuff,” you’ll find the good is hugely outweighed by the bad. As I’ve written in the past, my opinion is somewhat pessimistic as to how much we can do about slowing, let alone stopping, mean warming. The jury is still out on that, and I profess no expertise on prescriptive remedies. That’s up to society and its leaders. I just try to lay out some of the evidence of what’s actually happening, and what’s more likely to happen in the future “standing on the shoulders” of other more accomplished scientists who have been doing the work.