The number caught my eye. Because of its immensity. Twenty-eight trillion tonnes. That is one hell of a lot of ice. On the 23rd of August, The Guardian reported that planet Earth had lost 28 trillion tonnes of ice since 1994. Slowly, over 30 years, it had melted away. It was lost from glaciers, from the ice caps on Greenland and Antarctica, from coastal Arctic lands, from ice shelves that can be a couple of hundred meters thick, rising like great, glistening cliffs around Antarctica or northern Canada, and from floating sea ice. Even from the upper reaches of Kilimanjaro. The Guardian was referring to a new paper now under review, for eventual publication in The Chryosphere. It appeared on-line on 14th August. In it, Tom Slater of University of Leeds, and seven colleagues from that and other UK climate science research groups, reported on a series of calculations they had made using satellite-derived measurements of ice mass across the planet collected since the early 1990s. These data were supplemented and confirmed with more direct measurements of ice loss in specific sites. They calculated that immense number.
So, how much is 28 trillion tonnes of ice anyway? A quick look at Google advised me that one cubic meter of ice weighs 919 kilograms. Reminding myself that one tonne equals 1000 kg, and that a trillion is a thousand billion (the aging brain needs these mini-refresher courses), I realized that if one had a column of ice, 100 meters square (a column about the size of a small city block in size), it would need to rise 3,046,789,989 meters into the sky to weigh 28 trillion tonnes. Assuming, of course, that the weight of ice did not melt, deform, or crush the bottom tiers, that 3 billion plus meters is roughly from here to the moon, and onward, eight times further. Some of that ice, the sea ice, has not contributed to sea level rise. But most of it has. And the melting did not stop in 2017 (the final date in the Slater group’s calculations). Yes, there remains a lot of ice on this planet, but the amount lost over those 30 years is still substantial – and most of us have been barely aware that it was happening.
The ability to simultaneously embrace two conflicting ideas is a strange human trait. In 1936, F. Scott Fitzgerald said, “The test of a first-rate intelligence is the ability to hold two opposed ideas in mind at the same time and still retain the ability to function.” He saw it as a valuable ability because ideas are usually biased by perspective and two apparently opposed ideas could be two different perspectives on a topic. With more than one perspective you have greater options for effective action.
But what about the ability to cling to two conflicting ideas that are truly incompatible – say the idea that the Earth is flat and the idea that it is a sphere floating in space? Or the idea that climate is only changing trivially or scarcely at all, and the idea that climate change is an existential threat to humanity? Each idea may be supported by evidence, but they cannot both be correct. The evidence supporting one is misleading.
I think we have long since reached the point where the evidence supporting an argument that the changes we are seeing on this planet are merely natural variability around some average state – that evidence now pales into insignificance when contrasted with the abundant and growing evidence that the world’s climate is changing dramatically. And yet, many of us continue to act as if climate change will only be a minor inconvenience, a triviality, compared to all those other truly important things that affect our lives – stock market gyrations, political unrest, income inequality, Presidential tweets. This clinging to a belief that climate change will turn out to be ‘no big deal’ is not a mark of intelligence; it may be a sign of Pollyannaism run amok. The sad fact is that whole governments are operating as if the climate crisis is a minor impediment to carrying on as usual. It isn’t, and that column of ice stretching far beyond the moon shows how un-trivial climate change is.
The coral reefs of the world first delivered a mass bleaching event during the strong el Niño of 1982-83; reefs throughout the Galapagos, along the Pacific coast of Panama, and at some points north and south bleached severely. The Galapagos reefs have never recovered. Reefs delivered the first circumtropical mass bleaching episode during the even stronger el Niño of 1997-98, and they have continued to bleach intermittently. Now the Great Barrier Reef has been hit by three severe bleaching events in 2016, 2017-18 and 2020 – only the 2016 event occurred during a strong el Niño. Bleaching events are becoming more frequent and are less strongly tied to major el Niños than they were originally (see my comments here and earlier). The global pattern is clear: something novel is happening, and it is happening more frequently year by year. That novel thing is our warming of the planet and coral reefs have been shouting about it for almost forty years. It is now apparent that the glaciers, the ice caps, the shelves and sea ice have also been shouting in their own quiet but inexorable way. This world is warming fast, and the warming is changing the nature of the planet. The world has been without stores of ice in the past, and its been without coral reefs in the past. But at times when the world lacked reefs, or ice, it was a very different place to now, a place ill suited to sustaining our immense human economy.
Recent research reports make clear that the melting of ice has broad implications for the functioning of marine ecosystems, the productivity of marine fisheries, and the biodiversity of polar and alpine ecosystems. The melting also has implications for global weather patterns, global ocean circulation, and most importantly for the rate of future climate warming. The recent report from the Canadian Department of Fisheries and Oceans (DFO) on the state of the Canadian Arctic sets out clearly the importance of ice to Arctic environments, and how loss of ice is leading to dramatic changes in Arctic ecosystems. Some of these changes may be positive, in the sense they will maintain or enhance opportunities for life, but many will be negative. Unfortunately, our relative lack of understanding of how Arctic ecosystems function precludes any certainty on this topic.
Vast ice shelves many meters thick and extending kilometers from shore have long been a feature of polar landscapes. The ice is permanent, in that it has been there for thousands of years. And the ice supports an ecosystem adapted to its special features. Now, Arctic ice shelves have largely disappeared. The Milne Ice Shelf, on the northwest coast of Canada’s Ellesmere Island, was the last intact ice shelf in the Canadian Arctic until July 31st when it began to break up. By August 6th, it had lost over 40% of its area as two large pieces (the bigger about the size of Manhattan Island) floated away. Loss of ice shelves forces a reorganization of coastal ecosystems, disrupts the access by people to sea ice and the hunting that provides, and increases erosion of shorelines by ocean waves.
Recently, Mercé Casas-Prat and Xiaolan Wang of Environment and Climate Change Canada published results of their analysis of the effects of the loss of sea ice on wave height in the Arctic. As summarized by the Globe and Mail, their article in Geophysical Research: Oceans modelled changes in periodicity and height of oceanic swells and coastal waves as climate change removes ice during the rest of this century. They found open the average height of ocean swells could increase by almost six meters by 2080-2100, while coastal waves could grow by two meters. These changes in average conditions will disrupt shipping and lead to widespread coastal erosion. Canadian towns like Tuktoyuktak are already experiencing serious erosion that threatens infrastructure.
A more dynamic ocean will likely also hasten the breakup of sea ice, providing a positive feedback to warming and further storminess. As Glenn Macgillivray wrote in the Globe and Mail on August 19th, it is clear as ice that ‘the Arctic is unravelling’.
Figure 2 from the Science article by K.M. Lewis and colleagues shows (top graph) that while the extent of open water in the Arctic has increased since 1998, the rate of increase is now slowing. Yet the rate of primary production (bottom graph) continues a near-linear upward trend. The middle graph reveals that the density of phytoplankton in the water column was almost unchanged through the early 2000s but has been increasing dramatically since 2008. Image © Science magazine.
One of the changes in the Arctic which might be positive is an increase in primary production – the photosynthesis by phytoplankton is increasing because the surface waters are warmer, the loss of ice is allowing light to penetrate further, and, in coastal areas, there is enhanced nutrients available because of the enhanced erosion. As Stanford University’s K.M. Lewis and colleagues describe in their July 10th article in Science, there is considerable uncertainty in future trends in production because of the complex interactions among nutrients, water temperature, salinity, ice extent and storminess. Their data reveal that while the increase in production was explained almost entirely by the increase in open water between 1998 and 2008, the increase since then has been due to an increase in the density of phytoplankton in the water column. That increase in density can only be sustained by an increase in nutrients available, an increase which has likely been due to inputs via coastal erosion. In the future, warmer and less saline surface waters may become sufficiently segregated from cooler, saltier, more nutrient-rich deeper waters curtailing the provision of nutrients to the phytoplankton. Conversely, the stronger ocean swells and stormier weather anticipated may facilitate continued, or even enhanced delivery of nutrients from deeper waters. Whatever the future trend, the substantial increase in productivity that has occurred over the past twenty years, and which will continue for at least the near future, has implications for fisheries production, and maintenance of Arctic biodiversity.
These changes in polar environments are being reported at a time when our confidence in the projections of future climate change is growing. Any projection of a system’s state into the future, particularly for a complex system such as Earth’s climate, will entail some uncertainty. Even the best models will never be able to account precisely for every butterfly wing flap that plays a role in determining our future climate. As a result, we have gotten used to viewing projections of future temperature, rainfall, windspeed and so on as a mean projection, the best estimate, surrounded by an increasingly broad cone of possible futures for the measurement in question. The best models provide the narrowest cones of uncertainty, and the good news is that the recent results of what is called the World Climate Research Programme (WCRP) have dramatically narrowed the uncertainty around future climate projections.
The improvement in estimates of climate sensitivity achieved in the WCRP study. Image © Science.
Ever since 1979 when efforts to estimate the effects of CO2 on climate began in earnest, climate scientists have referred to ‘climate sensitivity’ — the likely average global temperature increase for a doubling of the CO2 concentration in the atmosphere. This is a useful index for climate change, given that we have already increased atmospheric CO2 from the preindustrial ~280 ppm to above 417 ppm in the final week of May 2020. That’s about a 49% increase or half a doubling. But since 1979, the estimated climate sensitivity has stubbornly sat at about 1.5o to 4.5oC. That is an enormous range, from an inconvenience to a disaster if it happened, but climate scientists could not do better, and we all had to remember that projections of climate contained this considerable uncertainty.
The efforts of the consortium within WCRP have reduced that uncertainty. Now the world’s climate sensitivity is estimated as between 2.6o and 3.9oC. What this means is that if we continue to add CO2 as we certainly will, at least in the sort term, and if atmospheric CO2 approaches 560 ppm, as it easily could, the average global temperature could increase between 2.6o and 3.9oC above preindustrial levels. That increase still poses real problems for us and for the biosphere, but the extent of those problems is estimated much more precisely. Which means that planning for adaptation and mitigation can proceed with greater certainty about what we will be up against in coming decades.
One thing’s for sure though. Climate is changing, and the idea that the coming changes will have trivial effects is clearly incorrect. The tropics and the Arctic are both changing dramatically now. The world will be changing dramatically long before we get to 2100 unless we get serious about containing climate change. Keeping the average global temperature increase to within 1.5oC above preindustrial temperatures is still an important and appropriate goal that we, collectively, have yet to get solidly behind. It represents the amount of warming likely with less than a 50% increase in CO2 concentration from the preindustrial 280 ppm. In other words, once the warming effects of the CO2 already in the atmosphere are fully realized, we are pretty well there – meaning there is absolutely no time to lose in cutting emissions. We knew this was the case back in 2015!
The results of the new WCRP work to refine the estimate of climate sensitivity mean that the science is even more certain of this than it was before. And that is why the current dithering of politicians of all shapes, sizes, and political stripe should be particularly concerning to all of us.
Climate change is real. The biosphere is shouting out that we face a real emergency. The science is better refined than ever before, so we have real certainty about what is coming and what we need to do. And yet… politicians continue to hold onto their belief that ‘maybe things won’t get too bad’ or ‘maybe some small adjustments will suffice’. Sort of like suggesting that the covid-19 pandemic will fade away any time now all by itself.
It’s way past time to act on climate change! Image ©Olivia Vanni/AP