Ultimately, we'll all realize that there is no such thing as a climate-safe place, only places with different climate-related impacts, unfolding on different timescales, to differently-equipped people, interconnected in ways we can't begin to fathom. Jamie Beck Alexander Project Drawdown
NOAA provided a summary of a study published in the Proceedings of the National Academy of Sciences of the United States of America. In a nutshell, the climate niche where we can survive is called a Goldilocks Zone, neither too hot nor too cold, which continues to move poleward.
Humans, the vast majority of which reside in lower latitudes, will have increased their populations significantly. As a result, there will be a mismatch between a livable climate and distributed people. There will be terrors that we had never had to face before as temperatures conducive to creating civilization as we know it today turn into a dangerous threat.
From NOAA: (see map in the above cover photo)
The human climate niche are areas on Earth where humans have historically lived due to favorable climate conditions related to temperature and precipitation. For the past 6000 years, humans have mostly lived in the same climate conditions as they do now. In addition to humans, this climate niche is also where the production of crops and livestock typically takes place. The optimal mean annual temperature of this identified niche is around 52 °F to 59 °F (∼11 °C to 15 °C). But as the climate changes, the areas that fit within the human climate niche will change as well. This dataset identifies the current human climate niche, with land shaded to show which areas are more or less suitable for people, and then projects the future human climate niche in 2070 based on the climate projection scenario of RCP 8.5. Also included as an additional layer that can be turned on and off is a map that shows the areas where the mean annual temperature is greater than 84 °F (29 °C). Currently, only 0.8% of the global land surface has a mean annual temperature greater than 84 °F, but in 2070 that is projected to cover 19% of the global land and impact an estimated 3.5 billion people.
According to the researchers who developed this dataset, “The bottom line is that over the coming decades, the human climate niche is projected to move to higher latitudes in unprecedented ways. At the same time, populations are projected to expand predominantly at lower latitudes, amplifying the mismatch between the expected distribution of humans and the climate.” The researchers estimate that roughly 30% of the projected global population would have to move if people were to live in the human climate niche as they do now. They further suggest that “each degree of temperature rise above the current baseline roughly corresponds to one billion humans left outside the temperature niche, absent migration” for the socioeconomic SSP3 scenario.
The SSP3, which NOAA refers to is Socioeconomic Shared Pathways, and 3 is the direst. And, according to Murphy's law, that is where we are heading if we do not cut emissions to zero.
It is described in a 2015 paper as:
“A resurgent nationalism, concerns about competitiveness and security, and regional conflicts push countries to increasingly focus on domestic or, at most, regional issues. This trend is reinforced by the limited number of comparatively weak global institutions, with uneven coordination and cooperation for addressing environmental and other global concerns. Policies shift over time to become increasingly oriented toward national and regional security issues, including barriers to trade, particularly in the energy resource and agricultural markets... A low international priority for addressing environmental concerns leads to strong environmental degradation in some regions. The combination of impeded development and limited environmental concern results in poor progress toward sustainability. Population growth is low in industrialized and high in developing countries. Growing resource intensity and fossil fuel dependency along with difficulty in achieving international cooperation and slow technological change imply high challenges to mitigation. The limited progress on human development, slow income growth, and lack of effective institutions, especially those that can act across regions, implies high challenges to adaption for many groups in all regions.”
Almost every single lifeform on earth has lived through the most stable climate window in 650,000 years, according to Peter Brannen writing in The Atlantic earlier this year. He notes that only 10,000 years ago, large species of mammals were driven to extinction by the hands of early humans.
Nine thousand years ago, humans began to stop wandering for food and began agriculture. Mexico, the Fertile Crescent, China, and the Andes developed communities where trade and arts flourished. Brannen goes back in the record of the planet's rocks and is a read not to be missed.
But sapiens has mucked up our atmosphere by burning fossil fuels over just a couple of centuries. The result has been increasing temperatures with conditions that had become more humid and hot than when we first evolved. We are beginning to see the consequences today, a climate that is alien and hostile to life.
Brannen is a planetary scientist. His stories include "astrobiology, paleoclimate, paleontology, geology, geochemistry, marine biology, the philosophy of science, and evolutionary biology." The New Yorker described his work — "Brannen demonstrates, fossils are useful for more than just fuel: they can teach us how not to die."
The first couple of steps back in time won’t take us to a warmer world—but they will illuminate just what sort of ill-tempered planet we’re dealing with. As we pull back even slightly from the span of recorded history—our tiny sliver of geologic time—we’ll notice almost at once that the entire record of human civilization is perched at the edge of a climate cliff. Below is a punishing ice age. As it turns out, we live on an ice-age planet, one marked by the swelling and disintegration of massive polar ice sheets in response to tiny changes in sunlight and CO2 levels. Our current warmer period is merely one peak in a mountain range, with each summit an interglacial springtime like today, and each valley floor a deep freeze. It takes some doing to escape this cycle, but with CO2 as it is now, we won’t be returning to an ice age for the foreseeable future. And to reach analogues for the kind of warming we’ll likely see in the coming decades and centuries, we will need to move beyond the past 3 million years of ice ages entirely, and make drastic jumps back into the alien Earths of tens of millions of years ago. Our future may come to resemble these strange lost worlds.
We know there will be devastating impacts from this current climate emergency. Global heating today is killing our natural CO2 sinks such as forests and sea-grass, melting our freshwater supply locked in the ice of the poles and mountain ranges, fueling droughts and climate famine, and sea-level rise.
Some of the models are starting to catch up. In 2019, one of the most computationally demanding climate models ever run, by researchers at the California Institute of Technology, simulated global temperatures suddenly leaping 12 degrees Celsius by the next century if atmospheric CO2 reached 1,200 ppm—a very bad, but not impossible, emissions pathway. And later that year, scientists from the University of Michigan and the University of Arizona were similarly able to reproduce the warmth of the Eocene by using a more sophisticated model of how water behaves at the smallest scales.
The paleoclimatologist Jessica Tierney thinks the key may be the clouds. Today, the San Francisco fog reliably rolls in, stranding bridge towers high above the marine layer like birthday candles. These clouds are a mainstay of west coasts around the world, reflecting sunlight back to space from coastal California and Peru and Namibia. But under higher-CO2 conditions and higher temperatures, water droplets in incipient clouds could get bigger and rain down faster. In the Eocene, this might have caused these clouds to fall apart and disappear—inviting more solar energy to reach, and warm, the oceans. That might be why the Eocene was so outrageously hot.
This sauna of our early mammalian ancestors represents something close to the worst possible scenario for future warming (although some studies claim that humans, under truly nihilistic emissions scenarios, could make the planet even warmer). The good news is the inertia of the Earth’s climate system is such that we still have time to rapidly reverse course, heading off an encore of this world, or that of the Miocene, or even the Pliocene, in the coming decades. All it will require is instantaneously halting the super-eruption of CO2 disgorged into the atmosphere that began with the Industrial Revolution.
Subtropical life may have been happy in a warmer Eocene Arctic, but there’s no reason to think such an intimately adapted ecosystem, evolved on a greenhouse planet over millions of years, could be reestablished in a few centuries or millennia. Drown the Florida Everglades, and its crocodilians wouldn’t have an easy time moving north into their old Miocene stomping grounds in New Jersey, much less migrating all the way to the unspoiled Arctic bayous if humans re-create the world of the Eocene. They will run into the levees and fortifications of drowning Florida exurbs. We are imposing a rate of change on the planet that has almost never happened before in geologic history, while largely preventing life on Earth from adjusting to that change.
Taking in the whole sweep of Earth’s history, now we see how unnatural, nightmarish, and profound our current experiment on the planet really is. A small population of our particular species of primate has, in only a few decades, unlocked a massive reservoir of old carbon slumbering in the Earth, gathering since the dawn of life, and set off on a global immolation of Earth’s history to power the modern world. As a result, up to half of the tropical coral reefs on Earth have died, 10 trillion tons of ice have melted, the ocean has grown 30 percent more acidic, and global temperatures have spiked. If we keep going down this path for a geologic nanosecond longer, who knows what will happen? The next few fleeting moments are ours, but they will echo for hundreds of thousands, even millions, of years. This is one of the most important times to be alive in the history of life.
I have almost 200 diaries in draft form; this was one of them. I began thinking about the topic in August. It is why you can’t tip the tip jar if you are so inclined.