The amount of CO₂ in the atmosphere is currently approaching 430 parts per million. The last time there was this level of CO₂ in the atmosphere was during the Oligocene era, 23 to 33 million years ago, eons before humanity appeared on Earth. During that era, global average temperatures were 5 to 7 degrees Centigrade above our current historical average.

It’s curious that, even though carbon in the atmosphere is the same now as it was in the Oligocene, planetary average temperatures have only risen by 1.2 degrees, which is much less than the temperature of that historic era.

Why the difference? It’s because for various reasons there is a time lag between CO₂ emissions and their full warming effect. This time lag is a good 50 years for surface temperatures, and longer for the ‘warming’, or melting, of ice.

We currently have 1.2 degree of warming, and the climate changes we are experiencing reflect the effects of that 1.2 degrees, but we can be sure that this is just the tip of the climate iceberg. That’s because the Oligocene tells us in no uncertain terms what the eventual effect of the carbon we have emitted to date will be. It will likely take all of those 50 years or more for the climate to catch up, but catch up it will.

Given that humanity shows no sign of stopping CO₂ emissions anytime soon, and that CO₂ extractive technologies are very much in their infancy, we can confidently assume that a further 4 to 6 degrees of warming, perhaps more, is already baked into the Earth system, even if all emissions stopped today. The IPCC, a relatively conservative climate body, has considered for the last 15 years that a 6 degree rise in temperature is quite plausible.

On the face of it, that doesn’t seem too alarming. After all, temperature changes of this magnitude happen between day and night or summer and winter over most of the Earth. What we don’t really comprehend is that these familiar changes in temperature take place within a steady climate, one that is relatively stable over time.

But when the average temperature of the entire Earth changes by those few degrees, the whole Earth enters a vastly different range of climate zones.

Humans tend to trust direct experience much more than something they’ve been told. Because our direct experience is that the climate we see and feel has not changed all that much, we have been lulled into the illusion that 430 ppm of CO₂ is not so terrible. Sure, it’s been a little warmer, and there have been some bad floods, fires and droughts, but basically things feel much the same as they always have. We still have sun and rain, winter and summer, and geese flying north in the Spring.

In addition to our tendency to give priority to what our senses tell us, the news media has done almost nothing to dispel our illusions. They have done us a huge disservice by not making it clear that this is only the beginning of the warming and the climate catastrophe that this much CO₂ will cause. They also do us a great disservice when they report predicted increases in global temperature but do not tell us what the Earth will actually be like at those temperatures. Most people on Earth are truly unaware of where we are headed.

So what will the Earth and her climate actually be like as atmospheric carbon relentlessly, step by step, forces the temperature to rise to Oligocenic levels?

To answer this question, I turned to the extensively researched book by Mark Lynas, Six Degrees of Climate Emergency: Our Final Warning. Mark has examined both the latest climate science and Earth’s Paleoclimate record, the record of past climates preserved in ice cores, sediment cores and fossil records, to predict in great detail the likely state of the Earth and the state of the climate as we move from from 2 to 6 degrees of warming.

What follows is a summary, degree by degree, of his findings. I personally find them terrifying, but see for yourself.

Two Degrees

Arctic sea ice disappears in summer, adding to the feedback loop of even greater warming in the Arctic, and exacerbating extreme droughts and floods worldwide. Permafrost melting, a potent source of methane, increases and releases 60-70 billion tonnes of carbon, further accelerating climate breakdown. Irreversible loss of the West Antarctic ice sheet begins. 136 megacities are at least partly underwater, along with the homes of 79 million people and many atoll nations, with total flood damage costs of $1.4 trillion per year. Cereal harvests fall by at least 25% due to drought, periods of extreme heat and greater pest damage. At least half a million people die from malnutrition and starvation. People also die from heatstroke as 20 of the world’s megacities see deadly levels of heat for some part of each year. Loss of glacial meltwater reduces water supplies for at least a billion people. Hurricanes and cyclones are more intense. Monsoons become wetter, and severe flooding is more likely everywhere. There is a 20% increase in drought globally, most extreme in the Amazon, killing trees and increasing wildfires. Mammals, birds and reptiles lose 25% of their range while plants, insects and amphibians lose 33%. Almost all coral reefs are dead or dying, and the 25% of sea creatures that depend on reefs for their existence are largely extinct. Mangrove forests and seagrass meadows are dying, taking with them all organisms that depend on the habitat they provide.

Human societies still survive in some semblance of their current condition, but just one more degree will bring our civilization to the edge of collapse.

The Paleoclimate record suggests that two degrees of warming, bad as it is, may also be a climate tipping point beyond which temperatures rise rapidly, uncontrollably and irreversibly.

Three Degrees

33% of global land area, and 50% of humanity are exposed to deadly heat for 20 or more days per year. Asia is in the ‘extremely dangerous’ heat zone. African cities face 20-50 times more dangerous heat days than now. US cities have annual heatstroke deaths in the thousands. Drylands cover half the global land surface.  Temperatures cross critical thresholds in all major food production areas. Even as far north as Canada, crops are scorched by extreme heat. Famines kill millions and create millions more refugees. Himalayan glaciers and their essential meltwaters are reduced by half. Most ice disappears in the Andes. Flood damages from meltwater and storm deluges rise by more than 1,000%. There is an emerging mass extinction of all life on Earth. In North America, 67% of bird species are gone or facing extinction. The Amazon is in full-scale collapse, ravaged by megafires which pour billions of tonnes of carbon into the air. Four and a half million square miles (12 million square kilometers) of permafrost melt, releasing unknown quantities of methane.

Sea level is 5 feet (1.7 m) higher than today, displacing hundreds of millions of people. Coral reefs are gone, and marine heatwaves take a deadly toll on all remaining marine ecosystems.

Human societies, already extremely stressed, face complete collapse with another degree of heat.

Four Degrees

The Gulf region, South Asia, and eastern and northern China, are biologically unsurvivable for all warm-blooded animals, including ourselves. Southern Europe, Central America, Brazil, mainland Australia and southern China are deserts. The southern states of the US look like Death Valley does now.  All remaining northern forests are consumed by huge fires which create their own fire tornadoes, cumulus clouds, and black hail. The Earth is covered in a layer of ash and dust as though there has been a nuclear war. With little snowfall remaining, torrential rains pound mountain ranges, causing megafloods that submerge whole cities in a matter of hours. The only suitable areas for crops are Siberia and Arctic Canada. The international trade in food crops collapses, and famine is now a central part of the human experience. Billions flee unlivable land, pouring over national borders and overwhelming any functioning cities. Coastal areas are ravaged by Category 6 superstorms. Toxic algal blooms affect most coastlines, already irretrievably altered by a 10 foot (3 meter) rise in sea level.

Most of the planet’s surface is now outside the evolutionary conditions of plants and animals, and this becomes the worst mass extinction since the end of dinosaurs, 65 million years ago.

Five Degrees

It is almost game over. Much of the planet is a wasteland of rocky continents surrounded by stagnant oceans, and 90% of habitable land is gone. All tropical and sub-tropical areas, including the oceans, experience year-round deadly temperatures. Apart from microbes, vast areas are gradually becoming sterilized by heat shock. Ferocious hurricanes now reach the polar regions. Land surfaces are alternately scoured by dust storms and savage floods. Global food production is only possible in the highest mountain ranges, the highest latitudes and some continental margins. The few humans who survive are crammed into ‘refuges’ in areas such as Greenland and the Antarctic Peninsula. They find themselves in a silent world as wildlife is wiped out by intolerable heat. Those few species that have managed to survive are now 3000 miles (5000 km) from their original homes.

Six Degrees

A catastrophic failure of all Earth systems creates a hell on Earth. All forests are charred layers of ash. The ozone layer, depleted by oceanic eruptions of toxic gases, does not protect against the mutating effects of UV radiation, especially at the higher latitudes, the only place where life can exist. Marine mammals and most fish are dead. Only jellyfish and toxic algae proliferate, and only towards the poles. Arctic coastal shelves are torn apart by violent methane eruptions. Soils that once fed billions blow away in vast dust storms and are washed into the oceans. Cities that once housed billions are buried under drifting sand or submerged by rising seas.

This is the greatest mass extinction that has ever happened on Earth, greater even than the Great Dying, the end-Permian catastrophe that destroyed 90% of all species then on Earth.

Humans, even in their refuges, and even with all their ingenuity, may also not survive this level of warming and devastation.

But it gets worse. It is possible that 6 degrees of warming may trigger a runaway greenhouse effect that eventually evaporates all water on Earth, thus eliminating all possibility of a new resurgence of life. The planet would be a lifeless Venus, a rocky hellscape, a billion years before time. The sixth extinction may turn out to be the final great extinction on Earth, not just the sixth but the very last of the Earth’s great dyings.

Now you know. This is the risk we are running. These are the odds we face.

The Buddhists have always made a practice of meditating on the inevitability of death. We will all die at some point, and it is useful for us each to prepare. But the death we may face as a planet is immeasurably vaster than the kind of death we have known so far, where death is something we think of that comes to each individually at the end of a normal lifespan. Perhaps we need also to start meditating on untimely death, mass death, and the death of most life on Earth.

 

Source

Mark Lynas, Six Degrees of Climate Emergency: Our Final Warning