تغییر اقلیم می تواند سلامت جوامع انسانی را از دو مسیر متاثر کند. نخست، رخدادهایی مثل موج های گرمایی یا سیل ها می توانند به صورت مستقیم بر سلامت انسان ها اثر بگذارند و دوم آنکه تغییر اقلیم می تواند به صورت غیرمستقیم مثلا از طریق کاهش محصولات کشاورزی روی سلامت انسان ها اثر بگذارد.
بر اساس مقاله ای که در سال جاری در PNAS منتشر شده است، بررسی تغییرات اقلیمی و رویدادهای اجتماعی در چند صدسال گذشته نشان می دهد که در حالی که جوامع انسانی قادر به سازگاری با تغییرات کوتاه مدت بوده اند و به جز در شرایط بسیار حاد توانسته اند با تغییرات کوتاه مدت کنار بیایند در حالی که در دوره های میان مدت و بلندمدت تغییرات اقلیمی اثرات نامطلوب متعددی از جمله بروز جنگ، افزایش فقر، گسترش بیماری ها و قحطی را به جای گذاشته است.
جدول زیر نتایج کلی مقاله را نشان می دهد:
| 1 | Long-term climate changes have often contributed to the decline of civilizations, typically via aridity, food shortage, famine, and unrest. |
| 2 | Medium-term climatic adversity, causing hunger, infectious disease outbreaks, poverty, and unrest, has often led to political overthrow. |
| 3 | Infectious disease epidemics have often accompanied or followed short-term and acute episodes of temperature shifts, food shortages, and social disruption. |
| 4 | Societies can build resilience and learn to cope with recurring shorter-term (decadal to multiyear) climatic cycles (e.g., El Niño Southern Oscillation, North Atlantic Oscillation) other than when extreme phases occur. |
| 5 | Weather disasters afflict both rich and (especially) poor populations. Recovery, sometimes with social reorganization, usually occurs. |
| 6 | The nexus of drought, famine, and starvation has been the major serious adverse climatic impact on health over the past 12,000 y. |
| 7 | Cold periods, more frequent and often occurring more abruptly than warm periods, have caused more apparent stress to health, survival, and social stability than has warming. |
| 8 | Historical experience shows that temperature changes of 1 to 2 °C (whether up or, more frequently, down) can impair food yields and influence infectious disease risks. Hence, the health risks in a future world forecast to undergo human-induced warming of both unprecedented rapidity and magnitude (perhaps well above 2 °C) are likely to be great. |
Source: http://www.pnas.org/content/109/13/4730/T3.expansion.html
McMichael, A. J. (2012). "Insights from past millennia into climatic impacts on human health and survival." Proceedings of the National Academy of Sciences 109(13): 4730-4737.
Climate change poses threats to human health, safety, and survival via weather extremes and climatic impacts on food yields, fresh water, infectious diseases, conflict, and displacement. Paradoxically, these risks to health are neither widely nor fully recognized. Historical experiences of diverse societies experiencing climatic changes, spanning multicentury to single-year duration, provide insights into population health vulnerability—even though most climatic changes were considerably less than those anticipated this century and beyond. Historical experience indicates the following. (i) Long-term climate changes have often destabilized civilizations, typically via food shortages, consequent hunger, disease, and unrest. (ii) Medium-term climatic adversity has frequently caused similar health, social, and sometimes political consequences. (iii) Infectious disease epidemics have often occurred in association with briefer episodes of temperature shifts, food shortages, impoverishment, and social disruption. (iv) Societies have often learnt to cope (despite hardship for some groups) with recurring shorter-term (decadal to multiyear) regional climatic cycles (e.g., El Niño Southern Oscillation)—except when extreme phases occur. (v) The drought–famine–starvation nexus has been the main, recurring, serious threat to health. Warming this century is not only likely to greatly exceed the Holocene's natural multidecadal temperature fluctuations but to occur faster. Along with greater climatic variability, models project an increased geographic range and severity of droughts. Modern societies, although larger, better resourced, and more interconnected than past societies, are less flexible, more infrastructure-dependent, densely populated, and hence are vulnerable. Adverse historical climate-related health experiences underscore the case for abating human-induced climate change.