A new article published in Science shows just how effective the opponents of solutions to human-caused climate change have been at sewing confusion. According to Climate Central,
Damon Matthews of Concordia University in Montreal and Susan Solomon of MIT, make the case that policymakers, the media, and to some extent the public have misunderstood the implications of two key concepts — the “irreversibility” of climate change, and the amount of global warming already in the pipeline due to historical greenhouse gas emissions.
The confusion comes from misunderstanding and misrepresentations of a study produced in 2010 by the National Research Council. This study noted that human civilizations will be stuck with the impacts of CO2 already put into the atmosphere for the next 1,000 years. What this means is that once we emit the carbon, it will keep doing its work to impact the climate for at least the next ten centuries. What this means is that current and past emissions result in irreversible impact.
Unfortunately, this statement has been misunderstood. Lawmakers, the media and members of the public have used this statement to make the logically false claim that human caused climate change is unstoppable and, therefore, nothing can be done about it. They have used this argument to support expanding greenhouse gas emissions at exactly the time they should be cut. These false claims and bad policies push us further down a path toward increasing damage and danger. And it appears that even the authors of these bad policies don’t have an inkling what they’re pushing for.
So we will attempt to clear up some of the confusion by providing you with a few illustrations of what happens if we stop emitting CO2 and greenhouse gasses (GHGs) now, if we stop emitting them in the future, and if we never stop emitting until it wrecks us.
What is most import when it comes to GHGs is when and if human emissions stop.
What the World Looks Like if Greenhouse Gas Emissions Stop Now
The absolute best case scenario we could hope for is that human CO2 and greenhouse gas emissions stopped today. This best case probably won’t happen. But we can, at least in concept, bask in the glow of the good future that could be if we were wise and ambitious enough to halt the burning of fossil fuels now.
According to scientific models produced by the IPCC, if worldwide greenhouse gas emissions were to stop today, global temperature increases would be brought to a standstill. The reason is, that at current levels of carbon in the atmosphere, there are still enough carbon sinks — primarily the ocean, to suck up a good degree of the carbon dioxide we’ve already put into the atmosphere. So CO2 concentrations fall over the course of the next 200 years until they stabilize at around 340 ppm CO2 (the red line in the graph shows what happens when human CO2 emissions drop to zero).
(Image source: here)
Now let’s look at temperatures. Because there are already a number of feedbacks to current warming already at work pushing the world to warm even further, the uptake of CO2 by world-wide carbon sinks doesn’t result in temperature decreases as one might think. Instead, we have global uptake of carbon pushing temperature down balancing with worldwide feedbacks pushing temperature up. The result is, according to the models, a worldwide stabilization of temperatures at nearly 1 degree C above the 19th century average.
In other words, a halt in emissions, according to this research, means putting the breaks on warming (red line shows both CO2 emissions and global temperature through 2300).
(Image source: here)
So according to this model projection, if human carbon emissions were to stop now, if all the automobiles, coal plants, natural gas plants, oil refineries, natural gas flaring, airplanes and every machine on Earth were to stop burning fossil fuels, then additional warming would probably stop now. But we’d be stuck with current temperature increases for a long, long time. Perhaps as long as 1,000 years. This cold turkey cutting of all CO2 emissions would, however, keep global temperatures in a range equal to the hottest averages during the Holocene, temperatures that would be far more easy for humans to adapt to than the additional warming that would come if human CO2 emissions continued, or worse, increased. (It is worth noting that some climate scientists and models show an increase in global warming of up to .8 degrees C even it emissions stop cold now. But even these models show further warming beyond the additional .8 degrees is halted.)
What this model data shows and the NRC paper confirms is that human caused temperature increases are stoppable but they are not reversible. A halt in CO2 emissions today stops temperature increases cold today. But we’re stuck with the warming we’ve already created.
The above scenario is the absolute best case we could hope for in our wildest dreams. For this reason, I’m going to call it the best case, least harm scenario. The reason being that if we halted CO2/GHG emissions now, we would only have to deal with the climate impacts we are dealing with now. That is, doubled number of intense storms, increased droughts in certain areas, increased water stress in certain regions, climate zones that are shifted 100 miles further north, reduced Arctic sea ice, and increased instances of wildfires in broad regions. These changes, though harmful, can probably be handled by world societies long-term without resulting in many reductions to human prosperity. On the other hand, such a massive, coodinated effort to reduce global greenhouse gas emissions and transition to new energy supplies would have far-reaching economic benefits.
Such a good result, perhaps, could happen if the world realized the severe dangers our current dependence on fossil fuel represents and shifted to an emergency transition footing for the world’s economies. Such a transition would have amazing benefits to the livelihoods of many, many people. It would result in much higher rates of employment, and with would radically transform the world’s teetering infrastructures. It would also ask for a serious commitment of resources from the rich and well off. For this reason, such a good result is unlikely to happen. The interests of the wealthy are, at best, divided between a benevolent group of public service minded elites and those bent on pursuing an irrational self interest. And the deadlock between these two groups makes the above best-case scenario all but impossible.
What the World Looks Like if Greenhouse Gas Emissions Stop Soon
Since the above, best case, of CO2/GHG emissions stopping now and temperatures stabilizing is unlikely to happen given the current world political climate, let’s look at the most likely, good, scenario. In this case, what happens to the world if CO2/GHG emissions stop soon?
By soon, we’ll practically look at how soon we could possibly begin to reduce worldwide CO2/GHG emissions on an ultimate path toward halting CO2/GHG emissions altogether. In this scenario, we’ll look at a range of possibilities. As we go forward, it is important to note that worldwide CO2/GHG emissions are currently increasing. So this makes the ‘good’ scenario we’re examining here very challenging in the current world political climate. What it involves is canceling a large number of oil, gas and coal megaprojects that, if they go forward would lock in, as climate scientist James Hansen puts it, “climate change game over.” It also involves replacing current fossil fuel infrastructure with an all alternative/renewable (or carbon capture) energy infrastructure by 2060 to 2065. Also by this time agriculture, construction and industry processes would all have to shift to a carbon-neutral footing.
In this scenario we’ll assume that worldwide CO2/GHG emissions begin to decrease in either 2020 or 2025 and eventually fall to zero by around 2060 or 2065. In the event of an early start to a decline in worldwide CO2/GHG emissions by 2020 and a total phase out of all CO2/GHG emissions by 2060, there is a 75% chance that we could halt temperature increases at 2 degrees Celsius above the 19th century average by 2100. If worldwide CO2/GHG emissions begin to decline in 2025 and halt by 2065, there is a 50% that worldwide temperatures are kept beneath the 2 degree Celsius threshold.
(Image source: here)
So aggressively beginning to reduce total worldwide CO2/GHG emissions by 2020 to 2025 and completely phasing out all fossil fuel burning by 2060 to 2065 would likely put the breaks on human caused global warming at slightly less than a 2 degree Celsius increase in temperatures above the 19th century average. This temperature increase would be greater than anything experienced in the last 200,000 years and would result in major changes to the world’s environment. Humans would probably be able to adapt to these changes with some difficulty. But the changes, though difficult, will probably be survivable and tolerable.
There is, however, one caveat. As humans push world temperatures closer to the 2 degrees Celsius and 450-500 ppm CO2 thresholds, the likelihood that global feedbacks to human warming will ramp up increases. What this means is that, at some point near these thresholds, the global environment may contribute its own emissions and physical changes that result in powerful additional warming. So it is possible that the above scenario may not reduce and eliminate emissions fast enough to prevent environmental changes from pushing global warming into a more dangerous range of 2, 3 or even 4 degrees above the 19th century average.
In this case, halting CO2/GHG emissions by 2060 to 2065 stops human caused global warming and feedbacks from pushing temperatures above a range of about 1.8 to 4 degrees Celsius above the 19th Century average. Because temperature increases in this range would be far greater and more damaging than those in a cold-turkey cessation of human CO2 emissions, I will call this the best hope, high risk emissions scenario. Best hope, because it is the best we can probably hope for or achieve given current politics, high risk because there is still substantial risk (25-50%) that temperatures will not remain below the ‘safe range’ of 2 degrees Celsius increases and because this scenario includes increasingly severe weather, climate and environmental damage for at least the next four decades.
What the best hope/high risk scenario prevents, however, is certain, terrible global catastrophe.
What the World Looks Like if Business As Usual Greenhouse Gas Emissions Continue
The last scenario we will look at is what happens if human greenhouse gas emissions continue indefinitely. It is important to note that this scenario will eventually come to pass even if human greenhouse gas emissions are reduced and only partially replaced by renewables or portionally mitigated by carbon capture. For the purposes of this scenario, however, we will consider that some replacement of fossil fuels by alternative energy sources occurs and that even some carbon capture and storage facilities are built. However, these new energy sources and mitigation technologies, though reducing the overall speed at which temperatures increase, do not result in the all important cessation of greenhouse gas emissions. In fact, because of overall growth in energy demand, greenhouse gas emissions continue to ramp up.
(Image source: The Australian Academy of Sciences)
In this scenario warming not only continues, it accelerates. By the end of the 21rst century, global average temperatures have increased by about 6 degrees Celsius. The result is that the world isn’t very livable for humankind. Even worse, feedbacks in the global climate render the world almost entirely uninhabitable with a 12 degree Celsius increase via feedback mechanisms by 2300.
Because failure to halt greenhouse gas emissions results in devastating warming we will call this scenario the catastrophic burn emissions scenario. In such a scenario, not only do climate conditions continue to worsen over the next four decades, as in the best hope/high risk scenario, they continue to worsen indefinitely and at a greater overall pace. Decade after decade sees increased damage and calamity. Eventually, civilizations will almost surely fail under a regime of increasingly harmful emergencies.
As such, the catastrophic burn scenario is an unconscionable consignment of posterity to a hellish world.
Understanding Greenhouse Gas Emissions is Simple: To Stop Warming, Stop Emitting
Though it is impossible to reverse the mild but still serious amount of warming already caused by past human greenhouse gas emissions, it is entirely possible to stop future warming. And in understanding this we also understand that:
1. The sooner we stop emissions, the less the world warms.
2. The sooner we stop emissions, the less in the way of dangerous climate change we will have to endure.
3. The sooner we stop emissions, the lower the risk that climate tipping points will be reached and the globe will contribute is own powerful warming mechanisms to the human warming brew.
4. If we don’t stop emissions, things will just keep getting worse and worse.
For these reasons, it should be imperative that we work as hard as we can to stop human greenhouse gas emissions as fast as we can. This is no longer just a matter of practicality and common sense. It is a matter of morality. For the sooner we stop greenhouse gas emissions, the more harm we prevent.