Greenhouse gas emissions have continued unabated in 2021, and there is no sign that countries will honor their commitments to reduce them anytime soon. This is evident as the West scrambles to find ways to replace Russian fossil fuel supplies as quickly as possible. This means fossil fuel emissions will not decline and we will reach a global average surface temperature 1.5 degrees Celsius above pre-industrial levels decades earlier than expected. Indeed, 1.5 degrees is the threshold which, according to climate science, indicates the point at which the effects of global warming will become irreversible and devastating, and will have profound consequences on the world’s ecosystems and on our global civilization.
These impacts are already severe and are rapidly worsening. Increasingly hot heat waves, more frequent and worsening storms, catastrophic floods, prolonged droughts, wildfires of unprecedented frequency and magnitude, continued acidification of the oceans and the consequent destruction of marine ecosystems, and a rate of species extinction 1,000 times the normal background rate is already wreaking havoc on planetary ecosystems and will only get worse. Feedback loops reinforce these devastating trends, and tipping points threaten to suddenly and quickly make them even deadlier.
All of this promises that, rather than a gradual effect on humanity, the impact of global warming on the human population could be rapid and catastrophic. The main aggravating factor will be human migration. As heat begins to become an existential threat to people in the tropics and subtropics, up to three billion people will migrate to temperate zones. This represents 40% of the human population, and its displacement will present an existential threat to populations in temperate zones. The inevitable consequence will be conflict on a scale that dwarfs all in human history.
This conflict, which will manifest itself at national borders throughout the world, could trigger the use of nuclear weapons which will make the loss of life even more devastating. The deterioration of the climate and this unprecedented level of conflict will reduce food production and distribution, which will further aggravate the loss of human life. As the pace of climate change continues to accelerate, this scenario is likely to play out in years, not decades, and therefore the decline in human population will be sudden rather than gradual. The following chart shows a potential scenario.
This graph shows two population scenarios. The blue line is the UN low population scenario. The orange line is a scenario that anticipates a drastic impact of climate change on the human population. It envisions a peak in the world’s population in 2030. Over the next decade, the scenario predicts that the population will decline by one billion as the rate of reproduction, even in developing countries, becomes negative and the rate global mortality rate will start to climb. Between 2040 and 2050, this scenario predicts a decrease in the global human population of more than six billion people as the human death rate soars due to the catastrophic effects of global warming, reduced food supplies, world war and the destruction of infrastructure and communications. upon which our world civilization depends.
It’s speculation. There is no certainty that this scenario will unfold on its own. But this is not an unreasonable speculation. Without a rapid and dramatic change in human behavior on a planetary scale, there is no reason to assume that we are safe from such a horrific fate.