This is the view from Kennedy airport 18,000 years ago: a two-mile high wall of ice (called the Laurentide Ice Sheet) extends across Canada and the northern part of the U.S. If you look south towards Jamaica Bay, there is only frozen tundra for as far as the eye can see. It is the exposed continental shelf. The seashore is 60 miles away because the oceans are 360 feet lower than they are today.
Forcings and Feedbacks
The Earth’s climate remains stable as long as the planet gives off as much energy as it absorbs. When this equilibrium is thrown out of balance, the Earth will either warm or cool until it comes back into equilibrium. Two factors are responsible for the balancing act: forcings and feedbacks.
A forcing is a trigger that throws the Earth’s energy balance out of equilibrium. Once that happens, various feedbacks (reactions to the forcing) kick in. Most of these reinforce the forcing. Feedbacks keep going until the Earth reaches energy equilibrium again.
Why did the Laurentide ice sheet melt? First, there was a forcing. In this case it was a slight change in the inclination of the Earth’s axis of rotation which caused a small increase in the amount of sunlight reaching the northern hemisphere. It wasn’t enough to melt the ice sheet, but it got the ball rolling.
Then there were three feedbacks. The first feedback was an increase in carbon dioxide (CO2). The oceans hold 50 times more CO2 than the atmosphere. Warm water can’t hold as much CO2 as colder water, so as the Earth got warmer, CO2 started coming out of the oceans and into the atmosphere. This made the Earth retain more heat, which made the oceans even warmer, which made them release more CO2 and so on in a self-reinforcing cycle.
The second feedback was an increase of water vapor in the air. As the air warms, it can hold more water vapor. Water vapor is a greenhouse gas. The more water vapor, the more greenhouse gas. The more greenhouse gas, the warmer the planet. The warmer the planet, the more water vapor and so in another self-reinforcing cycle.
The third feedback occurred when the glaciers began to melt. The ocean and the land are less reflective than ice. As the glaciers melted, less sunlight was reflected back into space. This made the Earth warmer, which melted more ice, which reduced the Earth’s reflectivity, which made it warmer and so on. Another self-reinforcing cycle. There are many other forcings and feedbacks that control the climate of the planet, which explains why climate science is so complicated.
Climate change is happening today because manmade CO2 and other greenhouse gases (gases that trap heat) are forcing the Earth’s energy equilibrium out of balance. The Earth must then adjust to this forcing by emitting more heat, and it can only do this by warming up. This process triggers feedbacks that accelerate this warming. The warming continues until energy equilibrium is reached. As long as we burn fossil fuels, energy equilibrium cannot be reached.
CO2 Emissions – 1751 to 2018
This graph is divided into four periods as the legend indicates. The numbers represent the annual amount of CO2 emitted at the beginning and end of each period. As you can see, the emission rate accelerated considerably around 1960. Today, annual CO2 emissions are close to 40 billion tons.
This graph shows the cumulative manmade CO2 emissions in each of the four periods shown in the previous graph. Cumulative emissions are important because CO2 stays in the air for thousands of years.
Nearly 80% of all man-made CO2 emissions have occurred since 1960, and half since 1990. These cumulative emissions have increased the CO2 concentration from 280 ppm to 411 ppm – a jump of 131 ppm. At the same time, the average global temperature has increased by 1°C (1 degree Celsius). For comparison, when the Earth emerged from the last glacial period 10,000 years ago, CO2 concentration increased by only 100 ppm and the global temperature increased by 5C. This was enough to melt the two-mile high glaciers, raise the level of the oceans by 360 feet, and vastly change the ecosystems of the world.
CO2 Emissions – 2020 to 2050
Global energy consumption is forecast to increase by 43% between 2020 and 2050. As energy consumption increases, so do emissions. Some of this demand will be met by a growing renewable energy industry. The rest will still require burning fossil fuels. The upshot is that annual CO2 emissions will increase by 23% by 2050, reaching 46.6 billion tons.
Based on this forecast, over the next 30 years an additional 1,250 billion tons of carbon dioxide will be emitted. The following chart shows the cumulative totals for each period.
The additional 1,250 billion tons of CO2 will raise the concentration of CO2 by 89 ppm from 411 ppm to 500 ppm – 1 ¾ times the pre-industrial concentration.
How will this affect global temperature? A precise forecast is impossible to make because so many factors are involved, but as the following two graphs show, the correlation between global temperature and CO2 concentration is very tight.
This graph shows CO2 and temperature over the past 800,000 years. During this time the Earth went through repeated glacial periods separated by brief interglacial periods (like the one we are in today). The graph shows that CO2 and temperature went up and down hand-in-hand. When it was warm, they went up, and when it was cold, they went down. Note the spike in CO2 levels (the dotted line on the right side of the graph). You can see that CO2 is now much higher than at any time in the last 800,000 years and that it is on a near-vertical trajectory. This is because it takes nature thousands of years to change the level of CO2 by the amount that we are changing it in just decades.
This graph shows the same correlation between CO2 and global temperature since 1880. As I noted previously, the global temperature is now 1C higher than the preindustrial average and increasing at an ever-faster pace.
Climate scientists who study the sensitivity of the global temperature to changes in CO2 concentration have determined that a doubling of CO2 will raise the global temperature by 3C. AT 500 ppm, CO2 concentration will be almost 80% of doubling the pre-industrial concentration. Prorating, this would result in a global temperature increase of 2.4C. This is well above both the 1.5C and 2C thresholds that the IPCC (Intergovernmental Panel on Climate Change) has declared will produce (1) very serious climate consequences and (2) catastrophic climate consequences.
A 2.4°C rise in global temperature will irrevocably disrupt the stable climate that has sustained civilization for the past 5,000 years. An unstable climate will wreak havoc with global civilization. As sea levels rise, coastal cities will become flooded. Millions will flee to higher ground, leaving homes and businesses behind. The cost in terms of infrastructure and lost business will be trillions of dollars. Coastal ports will also be flooded. This will impede international commerce and could essentially shut down the global economy.
As weather patterns worsen, more frequent and severe floods and droughts will reduce agricultural production. According to a 2017 abstract from the Proceedings of the National Academy of Sciences, every 1°C increase in global temperature will, on average, reduce global yields of wheat by 6.0%, rice by 3.2%, maize by 7.4%, and soybeans by 3.1%. A 2.4°C temperature increase would reduce global production of these crops by between 7% and 18%, depending on the crop. To compound matters, the UN predicts that, by 2050, the world population will increase from 8 billion to 10 billion. This combination of reducing crop yields and increasing population will make global famine a certainty.
Heat, flooding, disease, famine, increasing poverty, and the loss of government services will force tens to hundreds of millions of people to migrate from equatorial areas in the Asia-Pacific area, Africa, the Middle East, and Central and South America to cooler climates. Most of the world population lives in the northern hemisphere, so the bulk of the migration will be northward towards Europe, the US, and central Asia. The countries in these areas will be overwhelmed by these migrations and will resist it. The resulting conflicts could escalate to wars around the world – a world which still harbors 3,750 active nuclear warheads and another 10,000 inactive warheads. Millions will die from starvation, disease, or violence. At first, the tropics will bear the brunt of these effects, but as global temperature relentlessly rises, temperate zones will face the same consequences.
As apocalyptic as this scenario is, if we fail to end our fossil fuel emissions it will soon become a reality. We are already seeing unprecedented wildfires, flooding, and storms that are exacting billions in damages. These events will continue to increase in frequency and severity. At some point humanity will be forced to accept the reality that it has permanently altered the climate and made it more hostile to life, but by then it will be too late to avoid the worst-case scenarios. Even if the world started in earnest today to phase out fossil fuels, we are so dependent on them that it would take decades to do it.
And even if we do manage to phase out fossil fuels, we still have to reckon with past emissions. The planet will continue to warm to achieve energy equilibrium, and unless we remove these emissions, the equilibrium temperature will be unacceptably high. The technology exists, but it would take trillions of dollars to get back to 350 ppm, the level that the world’s foremost scientist on climate change says is the maximum that we can tolerate while avoiding catastrophic warming. And it will take energy – lots of it. If we cannot produce that energy with clean fuel sources, then we will need to burn more fossil fuels to remove the emissions, which would be like bailing water from the front to the back of the boat.
The environmental and social chaos that climate change will bring has already started. Just to take two examples, wildfires in California have been unprecedented in size and frequency over the past several years, and, as this is being written, the Australian navy is helping people evacuate from the mainland in order to flee epic wildfires which are unprecedented in terms of duration and intensity. There will be no single event or date which will signal a change from the normal, stable climate we are familiar with to the unstable and hostile one we are creating. It will continue to get worse at an ever-increasing pace until we find ourselves in the midst of it.
Climate scientists have consistently underestimated the speed at which the crisis is developing, in part because it is in the DNA of scientists to be cautious, and in part because alarming predictions are labeled “alarmist” by skeptics. And since we have never seen an apocalypse, except in the movies, society tends to accept this label. But the word “alarmist” means that the threat is being overstated. If the facts support the predictions, then, although the predictions may be alarming, they are not alarmist.
If we continue with business as usual, by 2030, the handwriting that scientists have been reading for decades will be on the wall for all to see, and by 2050, the worldwide environmental, economic, and social impact of climate change will likely be measured in trillions of dollars and millions of lives lost.
But we should not get too focused on the precision-timing of these forecasts. It is the inexorable trend that matters. Will it be any consolation if these events take another decade or two to materialize? Not to those who must live with them.
There are two contingencies that all the forecasts have excluded. One is the release of methane and the other is the collapse of the West Antarctic Ice Shelf. (The ice shelf is the part of a glacier that extends into the ocean.) If we continue burning fossil fuels, both are inevitable, and both will have profound effects. What is uncertain is when these events will occur. Given the rapid rate of melting that we are witnessing, they could occur within decades.
Permafrost and arctic continental shelves contain huge quantities of frozen methane. If they melt faster than expected (and so far, the permafrost is), they will release large amounts of methane which, during the first 20 years after its release, is 80 times more potent as a greenhouse gas than CO2. If this release is sudden and large (something which has happened in the geologic past in connection with mass extinctions), global warming will be dramatically accelerated.
The Antarctic Ice Shelf stabilizes the land-based glaciers in Antarctica and keeps them from flowing into the ocean. The West Antarctic Ice Shelf is being melted from beneath by warm water and is becoming unstable. If it should collapse, it will allow land-based glaciers to flow into the ocean, and if that happens, it will trigger an irreversible process that will accelerate the rise in sea level and ensure that it will continue for centuries.
Dance Until the Music Stops
In 2007, when asked by the Financial Times whether the investment risks his company was taking were too dangerous, Chuck Prince, CEO of Citibank, made the following statement:
“When the music stops, in terms of liquidity, things will be complicated. But as long as the music is playing, you’ve got to get up and dance. We’re still dancing.”
He meant that, even if Citigroup’s executives were worried that private equity valuations had gotten too risky and loan terms too loose, it would make little sense for them to pull back and forego all those underwriting fees because they were not sure when the markets would crash. So, they kept dancing. The following year the bubble burst and the world financial markets nearly collapsed. Only government bailouts saved them. Millions of innocent victims lost their homes and their life’s savings. Today the fossil fuel industry is doing the dancing, but the stakes are incomparably higher. And this time, there will be no government bailout.
Appendix: Emissions Calculations Based on EIA Energy Forecast
Note: CDIAC emissions and EIA calculated emissions overlap for the period 2010 to 2016. Average EIA emissions for this period are 5% higher than CDIAC emissions. Because CDIAC emissions are based on direct measurements and EIA emissions are calculated based on forecasted energy consumption, I reduced the EIA calculated emissions by 5% in order to provide a smooth transition. This gets us to the 1,250 billion tons shown in the graph. Since we are dealing with a forecast, this adjustment does not alter facts, and since the adjustment is minor, it does not affect the overall analysis.