The situation in Antarctica, both what’s currently being observed and the latest research, and the consequences are succinctly explained by Prof. Nerilie Abrahm from the Australian National University. Further consequences are discussed in the second half of the video.
By: Edward Doddridge, Research Associate in Physical Oceanography, University of Tasmania
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The rhythmic expansion and contraction of Antarctic sea ice is like a heartbeat.
But lately, there’s been a skip in the beat. During each of the last two summers, the ice around Antarctica has retreated farther than ever before.
And just as a change in our heartbeat affects our whole body, a change to sea ice around Antarctica affects the whole world.
Today, researchers at the Australian Antarctic Program Partnership (AAPP) and the Australian Centre for Excellence in Antarctic Science (ACEAS) have joined forces to release a science briefing for policy makers, On Thin Ice.
Together we call for rapid cuts to greenhouse gas emissions, to slow the rate of global heating. We also need to step up research in the field, to get a grip on sea-ice science before it’s too late.
One of the largest seasonal cycles on Earth happens in the ocean around Antarctica. During autumn and winter the surface of the ocean freezes as sea ice advances northwards, and then in the spring the ice melts as the sunlight returns.
We’ve been able to measure sea ice from satellites since the late 1970s. In that time we’ve seen a regular cycle of freezing and melting. At the winter maximum, sea ice covers an area more than twice the size of Australia (roughly 20 million square kilometres), and during summer it retreats to cover less than a fifth of that area (about 3 million square km).
In 2022 the summer minimum was less than 2 million square km for the first time since satellite records began. This summer, the minimum was even lower – just 1.7 million square km.
The annual freeze pumps cold salty water down into the deep ocean abyss. The water then flows northwards. About 40% of the global ocean can be traced back to the Antarctic coastline.
By exchanging water between the surface ocean and the abyss, sea ice formation helps to sequester heat and carbon dioxide in the deep ocean. It also helps to bring long-lost nutrients back up to the surface, supporting ocean life around the world.
Not only does sea ice play a crucial role in pumping seawater across the planet, it insulates the ocean underneath. During the long days of the Antarctic summer, sunlight usually hits the bright white surface of the sea ice and is reflected back into space.
This year, there is less sea ice than normal and so the ocean, which is dark by comparison, is absorbing much more solar energy than normal. This will accelerate ocean warming and will likely impede the wintertime growth of sea ice.
The Southern Ocean is a stormy place; the epithets “Roaring Forties” and “Furious Fifties” are well deserved. When there is less ice, the coastline is more exposed to storms. Waves pound on coastlines and ice shelves that are normally sheltered behind a broad expanse of sea ice. This battering can lead to the collapse of ice shelves and an increase in the rate of sea level rise as ice sheets slide off the land into the ocean more rapidly.
Sea ice supports many levels of the food web. When sea ice melts it releases iron, which promotes phytoplankton growth. In the spring we see phytoplankton blooms that follow the retreating sea ice edge. If less ice forms, there will be less iron released in the spring, and less phytoplankton growth.
Krill, the small crustaceans that provide food to whales, seals, and penguins, need sea ice. Many larger species such as penguins and seals rely on sea ice to breed. The impact of changes to the sea ice on these larger animals varies dramatically between species, but they are all intimately tied to the rhythm of ice formation and melt. Changes to the sea-ice heartbeat will disrupt the finely balanced ecosystems of the Southern Ocean.
Long term measurements show the subsurface Southern Ocean is getting warmer. This warming is caused by our greenhouse gas emissions. We don’t yet know if this ocean warming directly caused the record lows seen in recent summers, but it is a likely culprit.
As scientists in Australia and around the world work to understand these recent events, new evidence will come to light for a clearer understanding of what is causing the sea ice around Antarctica to melt.
If you noticed a change in your heartbeat, you’d likely see a doctor. Just as doctors run tests and gather information, climate scientists undertake fieldwork, gather observations, and run simulations to better understand the health of our planet.
This crucial work requires specialised icebreakers with sophisticated observational equipment, powerful computers, and high-tech satellites. International cooperation, data sharing, and government support are the only ways to provide the resources required.
After noticing the first signs of heart trouble, a doctor might recommend more exercise or switching to a low-fat diet. Maintaining the health of our planet requires the same sort of intervention – we must rapidly cut our consumption of fossil fuels and improve our scientific capabilities.
By: Christine Batchelor, Lecturer in Physical Geography, Newcastle University and Frazer Christie, Postdoctoral Research Associate, University of Cambridge
This article is republished from The Conversation under a Creative Commons license. Read the original article.
The Antarctic Ice Sheet, which covers an area greater than the US and Mexico combined, holds enough water to raise global sea level by more than 57 metres if melted completely. This would flood hundreds of cities worldwide. And evidence suggests it is melting fast. Satellite observations have revealed that grounded ice (ice that is in contact with the bed beneath it) in coastal areas of West Antarctica has been lost at a rate of up to 30 metres per day in recent years.
But the satellite record of ice sheet change is relatively short as there are only 50 years’ worth of observations. This limits our understanding of how ice sheets have evolved over longer periods of time, including the maximum speed at which they can retreat and the parts that are most vulnerable to melting.
So, we set out to investigate how ice sheets responded during a previous period of climatic warming – the last “deglaciation”. This climate shift occurred between roughly 20,000 and 11,000 years ago and spanned Earth’s transition from a glacial period, when ice sheets covered large parts of Europe and North America, to the period in which we currently live (called the Holocene interglacial period).
During the last deglaciation, rates of temperature and sea-level rise were broadly comparable to today. So, studying the changes to ice sheets in this period has allowed us to estimate how Earth’s two remaining ice sheets (Greenland and Antarctica) might respond to an even warmer climate in the future.
Our recently published results show that ice sheets are capable of retreating in bursts of up to 600 metres per day. This is much faster than has been observed so far from space.
Our research used high-resolution maps of the Norwegian seafloor to identify small landforms called “corrugation ridges”. These 1–2 metre high ridges were produced when a former ice sheet retreated during the last deglaciation.
Tides lifted the ice sheet up and down. At low tide, the ice sheet rested on the seafloor, which pushed the sediment at the edge of the ice sheet upwards into ridges. Given that there are two low tides each day off Norway, two separate ridges were produced daily. Measuring the space between these ridges enabled us to calculate the pace of the ice sheet’s retreat.
During the last deglaciation, the Scandinavian Ice Sheet that we studied underwent pulses of extremely rapid retreat – at rates between 50 and 600 metres per day. These rates are up to 20 times faster than the highest rate of ice sheet retreat that has so far been measured in Antarctica from satellites.
The highest rates of ice sheet retreat occurred across the flattest areas of the ice sheet’s bed. In flat-bedded areas, only a relatively small amount of melting, of around half a metre per day, is required to instigate a pulse of rapid retreat. Ice sheets in these regions are very lightly attached to their beds and therefore require only minimal amounts of melting to become fully buoyant, which can result in almost instantaneous retreat.
However, rapid “buoyancy-driven” retreat such as this is probably only sustained over short periods of time – from days to months – before a change in the ice sheet bed or ice surface slope farther inland puts the brakes on retreat. This demonstrates how nonlinear, or “pulsed”, the nature of ice sheet retreat was in the past.
This will likely also be the case in the future.
Our findings reveal how quickly ice sheets are capable of retreating during periods of climate warming. We suggest that pulses of very rapid retreat, from tens to hundreds of metres per day, could take place across flat-bedded parts of the Antarctic Ice Sheet even under current rates of melting.
This has implications for the vast and potentially unstable Thwaites Glacier of West Antarctica. Since scientists began observing ice sheet changes via satellites, Thwaites Glacier has experienced considerable retreat and is now only 4km away from a flat area of its bed. Thwaites Glacier could therefore suffer pulses of rapid retreat in the near future.
Ice losses resulting from retreat across this flat region could accelerate the rate at which ice in the rest of the Thwaites drainage basin collapses into the ocean. The Thwaites drainage basin contains enough ice to raise global sea levels by approximately 65cm.
Our results shed new light on how ice sheets interact with their beds over different timescales. High rates of retreat can occur over decades to centuries where the bed of an ice sheet deepens inland. But we found that ice sheets on flat regions are most vulnerable to extremely rapid retreat over much shorter timescales.
Together with data about the shape of ice sheet beds, incorporating this short-term mechanism of retreat into computer simulations will be critical for accurately predicting rates of ice sheet change and sea-level rise in the future.
By: Matthew England, Scientia Professor and Deputy Director of the ARC Australian Centre for Excellence in Antarctic Science (ACEAS), UNSW Sydney; Adele Morrison Research Fellow, Australian National University; Andy Hogg Professor, Australian National University; Qian Li Massachusetts Institute of Technology (MIT); Steve Rintoul CSIRO Fellow, CSIRO.
Republished in full from The Conversation under a Creative Commons license. See the original article: March 3, 2023
Off the coast of Antarctica, trillions of tonnes of cold salty water sink to great depths. As the water sinks, it drives the deepest flows of the “overturning” circulation – a network of strong currents spanning the world’s oceans. The overturning circulation carries heat, carbon, oxygen and nutrients around the globe, and fundamentally influences climate, sea level and the productivity of marine ecosystems.
But there are worrying signs these currents are slowing down. They may even collapse. If this happens, it would deprive the deep ocean of oxygen, limit the return of nutrients back to the sea surface, and potentially cause further melt back of ice as water near the ice shelves warms in response. There would be major global ramifications for ocean ecosystems, climate, and sea-level rise.
Our new research, published today in the journal Nature, uses new ocean model projections to look at changes in the deep ocean out to the year 2050. Our projections show a slowing of the Antarctic overturning circulation and deep ocean warming over the next few decades. Physical measurements confirm these changes are already well underway.
Climate change is to blame. As Antarctica melts, more freshwater flows into the oceans. This disrupts the sinking of cold, salty, oxygen-rich water to the bottom of the ocean. From there this water normally spreads northwards to ventilate the far reaches of the deep Indian, Pacific and Atlantic Oceans. But that could all come to an end soon. In our lifetimes.
As part of this overturning, about 250 trillion tonnes of icy cold Antarctic surface water sinks to the ocean abyss each year. The sinking near Antarctica is balanced by upwelling at other latitudes. The resulting overturning circulation carries oxygen to the deep ocean and eventually returns nutrients to the sea surface, where they are available to support marine life.
If the Antarctic overturning slows down, nutrient-rich seawater will build up on the seafloor, five kilometres below the surface. These nutrients will be lost to marine ecosystems at or near the surface, damaging fisheries.
Changes in the overturning circulation could also mean more heat gets to the ice, particularly around West Antarctica, the area with the greatest rate of ice mass loss over the past few decades. This would accelerate global sea-level rise.
An overturning slowdown would also reduce the ocean’s ability to take up carbon dioxide, leaving more greenhouse gas emissions in the atmosphere. And more greenhouse gases means more warming, making matters worse.
Meltwater-induced weakening of the Antarctic overturning circulation could also shift tropical rainfall bands around a thousand kilometres to the north.
Put simply, a slowing or collapse of the overturning circulation would change our climate and marine environment in profound and potentially irreversible ways.
The remote reaches of the oceans that surround Antarctica are some of the toughest regions to plan and undertake field campaigns. Voyages are long, weather can be brutal, and sea ice limits access for much of the year.
This means there are few measurements to track how the Antarctic margin is changing. But where sufficient data exist, we can see clear signs of increased transport of warm waters toward Antarctica, which in turn causes ice melt at key locations.
Indeed, the signs of melting around the edges of Antarctica are very clear, with increasingly large volumes of freshwater flowing into the ocean and making nearby waters less salty and therefore less dense. And that’s all that’s needed to slow the overturning circulation. Denser water sinks, lighter water does not.
Apart from sparse measurements, incomplete models have limited our understanding of ocean circulation around Antarctica.
For example, the latest set of global coupled model projections analysed by the Intergovernmental Panel on Climate Change exhibit biases in the region. This limits the ability of these models in projecting the future fate of the Antarctic overturning circulation.
To explore future changes, we took a high resolution global ocean model that realistically represents the formation and sinking of dense water near Antarctica.
We ran three different experiments, one where conditions remained unchanged from the 1990s; a second forced by projected changes in temperature and wind; and a third run also including projected changes in meltwater from Antarctica and Greenland.
In this way we could separate the effects of changes in winds and warming, from changes due to ice melt.
The findings were striking. The model projects the overturning circulation around Antarctica will slow by more than 40% over the next three decades, driven almost entirely by pulses of meltwater.
Over the same period, our modelling also predicts a 20% weakening of the famous North Atlantic overturning circulation which keeps Europe’s climate mild. Both changes would dramatically reduce the renewal and overturning of the ocean interior.
We’ve long known the North Atlantic overturning currents are vulnerable, with observations suggesting a slowdown is already well underway, and projections of a tipping point coming soon. Our results suggest Antarctica looks poised to match its northern hemisphere counterpart – and then some.
Much of the abyssal ocean has warmed in recent decades, with the most rapid trends detected near Antarctica, in a pattern very similar to our model simulations.
Our projections extend out only to 2050. Beyond 2050, in the absence of strong emissions reductions, the climate will continue to warm and the ice sheets will continue to melt. If so, we anticipate the Southern Ocean overturning will continue to slow to the end of the century and beyond.
The projected slowdown of Antarctic overturning is a direct response to input of freshwater from melting ice. Meltwater flows are directly linked to how much the planet warms, which in turn depends on the greenhouse gases we emit.
Our study shows continuing ice melt will not only raise sea-levels, but also change the massive overturning circulation currents which can drive further ice melt and hence more sea level rise, and damage climate and ecosystems worldwide. It’s yet another reason to address the
climate crisis – and fast.
Reprinted with permission from The Conversation
Matthew L. Druckenmiller, University of Colorado Boulder; Rick Thoman, University of Alaska Fairbanks, and Twila Moon, University of Colorado Boulder
In the Arctic, the freedom to travel, hunt and make day-to-day decisions is profoundly tied to cold and frozen conditions for much of the year. These conditions are rapidly changing as the Arctic warms.
The Arctic is now seeing more rainfall when historically it would be snowing. Sea ice that once protected coastlines from erosion during fall storms is forming later. And thinner river and lake ice is making travel by snowmobile increasingly life-threatening.
Ship traffic in the Arctic is also increasing, bringing new risks to fragile ecosystems, and the Greenland ice sheet is continuing to send freshwater and ice into the ocean, raising global sea level
In the annual Arctic Report Card, released Dec. 13, 2022, we brought together 144 other Arctic scientists from 11 countries to examine the current state of the Arctic system.
Some of the Arctic headlines of 2022 discussed in the Arctic Report Card.
NOAA Climate.gov
We found that Arctic precipitation is on the rise across all seasons, and these seasons are shifting.
Much of this new precipitation is now falling as rain, sometimes during winter and traditionally frozen times of the year. This disrupts daily life for humans, wildlife and plants.
Roads become dangerously icy more often, and communities face greater risk of river flooding events. For Indigenous reindeer herding communities, winter rain can create an impenetrable ice layer that prevents their reindeer from accessing vegetation beneath the snow.
Arctic-wide, this shift toward wetter conditions can disrupt the lives of animals and plants that have evolved for dry and cold conditions, potentially altering Arctic peoples’ local foods.
When Fairbanks, Alaska, got 1.4 inches of freezing rain in December 2021, the moisture created an ice layer that persisted for months, bringing down trees and disrupting travel, infrastructure and the ability of some Arctic animals to forage for food. The resulting ice layer was largely responsible for the deaths of a third of a bison herd in interior Alaska.
There are multiple reasons for this increase in Arctic precipitation.
As sea ice rapidly declines, more open water is exposed, which feeds increased moisture into the atmosphere. The entire Arctic region has seen a more than 40% loss in summer sea ice extent over the 44-year satellite record.
The Arctic atmosphere is also warming more than twice as fast as the rest of the globe, and this warmer air can hold more moisture.
Under the ground, the wetter, rainier Arctic is accelerating the thaw of permafrost, upon which most Arctic communities and infrastructure are built. The result is crumbling buildings, sagging and cracked roads, the emergence of sinkholes and the collapse of community coastlines along rivers and ocean.
Wetter weather also disrupts the building of a reliable winter snowpack and safe, reliable river ice, and often challenges Indigenous communities’ efforts to harvest and secure their food.
When Typhoon Merbok hit in September 2022, fueled by unusually warm Pacific water, its hurricane-force winds, 50-foot waves and far-reaching storm surge damaged homes and infrastructure over 1,000 miles of Bering Sea coastline, and disrupted hunting and harvesting at a crucial time.
Snow plays critical roles in the Arctic, and the snow season is shrinking.
Snow helps to keep the Arctic cool by reflecting incoming solar radiation back to space, rather than allowing it to be absorbed by the darker snow-free ground. Its presence helps lake ice last longer into spring and helps the land to retain moisture longer into summer, preventing overly dry conditions that are ripe for devastating wildfires.
Snow is also a travel platform for hunters and a habitat for many animals that rely on it for nesting and protection from predators.
A shrinking snow season is disrupting these critical functions. For example, the June snow cover extent across the Arctic is declining at a rate of nearly 20% per decade, marking a dramatic shift in how the snow season is defined and experienced across the North.
Even in the depth of winter, warmer temperatures are breaking through. The far northern Alaska town of Utqiaġvik hit 40 degrees Fahrenheit (4.4 C) – 8 F above freezing – on Dec. 5, 2022, even though the sun does not breach the horizon from mid-November through mid-January.
Fatal falls through thin sea, lake and river ice are on the rise across Alaska, resulting in immediate tragedies as well as adding to the cumulative human cost of climate change that Arctic Indigenous peoples are now experiencing on a generational scale.
The impacts of Arctic warming are not limited to the Arctic. In 2022, the Greenland ice sheet lost ice for the 25th consecutive year. This adds to rising seas, which escalates the danger coastal communities around the world must plan for to mitigate flooding and storm surge.
In early September 2022, the Greenland ice sheet experienced an unprecedented late-season melt event across 36% of the ice sheet surface. This was followed by another, even later melt event that same month, caused by the remnants of Hurricane Fiona moving up along eastern North America.
International teams of scientists are dedicated to assessing the scale to which the Greenland ice sheet’s ice formation and ice loss are out of balance. They are also increasingly learning about the transformative role that warming ocean waters play.
This year’s Arctic Report Card includes findings from the NASA Oceans Melting Greenland (OMG) mission that has confirmed that warming ocean temperatures are increasing ice loss at the edges of the ice sheet.
We are living in a new geological age — the Anthropocene — in which human activity is the dominant influence on our climate and environments.
In the warming Arctic, this requires decision-makers to better anticipate the interplay between a changing climate and human activity. For example, satellite-based ship data since 2009 clearly show that maritime ship traffic has increased within all Arctic high seas and national exclusive economic zones as the region has warmed.
For these ecologically sensitive waters, this added ship traffic raises urgent concerns ranging from the future of Arctic trade routes to the introduction of even more human-caused stresses on Arctic peoples, ecosystems and the climate. These concerns are especially pronounced given uncertainties regarding the current geopolitical tensions between Russia and the other Arctic states over its war in Ukraine.
Rapid Arctic warming requires new forms of partnership and information sharing, including between scientists and Indigenous knowledge-holders. Cooperation and building resilience can help to reduce some risks, but global action to rein in greenhouse gas pollution is essential for the entire planet.
Matthew L. Druckenmiller, Research Scientist, National Snow and Ice Data Center (NSIDC), Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder; Rick Thoman, Alaska Climate Specialist, University of Alaska Fairbanks, and Twila Moon, Deputy Lead Scientist, National Snow and Ice Data Center (NSIDC), Cooperative Institute for Research in Environmental Sciences (CIRES), University of Colorado Boulder
This article is republished from The Conversation under a Creative Commons license. Read the original article.
By: Maurice Huguenin, PhD Candidate, UNSW Sydney; Matthew England, Scientia Professor and Deputy Director of the ARC Australian Centre for Excellence in Antarctic Science (ACEAS), UNSW Sydney, and Ryan Holmes, Research fellow, University of Sydney
Republished in full from The Conversation under a Creative Commons license. See the original article: September 7, 2022
Over the last 50 years, the oceans have been working in overdrive to slow global warming, absorbing about 40% of our carbon dioxide emissions, and over 90% of the excess heat trapped in the atmosphere.
But as our research published today in Nature Communications has found, some oceans work harder than others.
We used a computational global ocean circulation model to examine exactly how ocean warming has played out over the last 50 years. And we found the Southern Ocean has dominated the global absorption of heat. In fact, Southern Ocean heat uptake accounts for almost all the planet’s ocean warming, thereby controlling the rate of climate change.
This Southern Ocean warming and its associated impacts are effectively irreversible on human time scales, because it takes millennia for heat trapped deep in the ocean to be released back into the atmosphere.
This means changes happening now will be felt for generations to come – and those changes are only set to get worse, unless we can stop carbon dioxide emissions and achieve net zero.
Ocean warming buffers the worst impacts of climate change, but it’s not without cost. Sea levels are rising because heat causes water to expand and ice to melt. Marine ecosystems are experiencing unprecedented heat stress, and the frequency and intensity of extreme weather events is changing.
Yet, we still don’t know enough about exactly when, where and how ocean warming occurs. This is because of three factors.
First, temperature changes at the ocean surface and in the atmosphere just above track each other closely. This makes it difficult to know exactly where excess heat is entering the ocean.
Second, we don’t have measurements tracking temperatures over all of the ocean. In particular, we have very sparse observations in the deep ocean, in remote locations around Antarctica and under sea ice.
Last, the observations we do have don’t go back very far in time. Reliable data from deeper than 700 metres depth is virtually non-existent prior to the 1990s, apart from observations along specific research cruise tracks.
To work out the intricacies of how ocean warming has played out, we first ran an ocean model with atmospheric conditions perpetually stuck in the 1960s, prior to any significant human-caused climate change.
Then, we separately allowed each ocean basin to move forward in time and experience climate change, while all other basins were held back to experience the climate of the 1960s.
We also separated out the effects of atmospheric warming from surface wind-driven changes to see how much each factor contributes to the observed ocean warming.
By taking this modelling approach, we could isolate that the Southern Ocean is the most important absorber of this heat, despite only covering about 15% of the total ocean’s surface area.
In fact, the Southern Ocean alone could account for virtually all global ocean heat uptake, with the Pacific and Atlantic basins losing any heat gained back into the atmosphere.
One significant ecological impact of strong Southern Ocean warming is on Antarctic krill. When ocean warming occurs beyond temperatures they can tolerate, the krill’s habitat contracts and they move even further south to cooler waters.
As krill is a key component of the food web, this will also change the distribution and population of larger predators, such as commercially viable tooth and ice fish. It will also further increase stress for penguins and whales already under threat today.
This largely comes down to the geographic set-up of the region, with strong westerly winds surrounding Antarctica exerting their influence over an ocean that’s uninterrupted by land masses.
This means the Southern Ocean winds blow over a vast distance, continuously bringing masses of cold water to the surface. The cold water is pushed northward, readily absorbing vast quantities of heat from the warmer atmosphere, before the excess heat is pumped into the ocean’s interior around 45-55°S (a latitude band just south of Tasmania, New Zealand, and the southern regions of South America).
This warming uptake is facilitated by both the warmer atmosphere caused by our greenhouse gas emissions, as well as wind-driven circulation which is important for getting heat into the ocean interior.
And when we combine the warming and wind effects only over the Southern Ocean, with the remaining oceans held back to the climate of the 1960s, we can explain almost all of the global ocean heat uptake.
But that’s not to say the other ocean basins aren’t warming. They are, it’s just that the heat they gain locally from the atmosphere cannot account for this warming. Instead, the massive heat uptake in the Southern Ocean is what has driven changes in total ocean heat content worldwide over the past half century.
While this discovery sheds new light on the Southern Ocean as a key driver of global ocean warming, we still have a lot to learn, particularly about ocean warming beyond the 50 years we highlight in our study. All future projections, including even the most optimistic scenarios, predict an even warmer ocean in future.
And if the Southern Ocean continues to account for the vast majority of ocean heat uptake until 2100, we might see its heat content increase by as much as seven times more than what we have already seen up to today.
This will have enormous impacts around the globe: including further disturbances to the Southern Ocean food web, rapid melting of Antarctic ice shelves, and changes in the ocean conveyor belt.
To capture all of these changes, it’s vital we continue and expand our observations taken in the Southern Ocean.
One of the most important new data streams will be new ocean floats that can measure deeper ocean temperatures, as well as small temperature sensors on elephant seals, which give us essential data of oceanic conditions in winter under Antarctic sea ice.
Even more important is the recognition that the less carbon dioxide we emit, the less ocean change we will lock in. This will ultimately limit the disruption of livelihoods for the billions of people living near the coast worldwide.
The carbon budget: a moving target that politicians just moved beyond reach.
Bankrupting the Carbon Budget:
In Bankrupting the Carbon Budget: Part I, tipping points were explained in Videos 1 and 2.
Others tipping points include wildfires in the Arctic and Australia. Together these released around 1Gt of CO2 in 2020. The devastation was so great in places that the conditions that led to the evolution of these ancient ecosystems no longer exist. ‘Zombie’ wildfires in boreal forests in Siberia and Canada and Alaska continue to burn peat underground over winter, re-igniting record-breaking forest fires in the summer of 2021.
These forests, which make up large parts of the biosphere that once absorbed carbon and locked it away, are now releasing carbon to the atmosphere together with human-caused emissions. They have passed a tipping point; a point of no return. The countdown clock in Fig. 1 doesn’t include these emissions because the compound effects are so complex, they have yet to be included in Earth systems models used by the Intergovernmental Panel on Climate Change (IPCC).
But the atmosphere doesn’t care where these emissions originate. Nor how much nations—most notably New Zealand—or businesses cheat on their carbon accounting. The reality is that the carbon budget is a globally shared account. Governments think they know how much we have left to ‘spend’, but the burning forests and melting permafrost and methane clathrates are making CO2 withdrawals over which we have no control. All we know is that somewhere between warming of 1-2°C, some tipping points will be irreversible and warming will accelerate, causing even more tipping points to fall like dominoes.
The relationship between the amount of CO2 in the atmosphere and warming is well-understood physics and chemistry. But there is a delay—a lag time of 10-20 years—between adding CO2 to the atmosphere and warming. So even if we switch off all emissions today, things will get hotter over the next two decades. It takes even longer for melting icecaps to raise sea levels, unless there’s an abrupt Meltwater Event (historically, these have raised sea levels as much as 4m/century).
The IPCC is banking our future existence on the lag time to literally buy us time to drawdown enough CO2 from the atmosphere and permanently store it back where it came from, with fingers crossed that will return the planet to a safe operating space of 350ppm.
The crucial thing about The Plan is that it depends entirely on assumptions. The most important assumption is that carbon capture technologies will draw down and safely store CO2 underground before warming triggers irreversible tipping points. This assumption (otherwise known as magical thinking) is because there isn’t enough land on Earth to plant enough trees to offset emissions while still being able to grow food to feed an exploding global population:
“No artificial machines that are even in the design stage will also clean our air, clean our water, provide habitat for wildlife and all the other useful features of trees.” – Sophie Bertazzo, Senior editor, Conservation International
As Bonnie Waring said in the quote above:
“If we absolutely maximised the amount of vegetation all land on Earth could hold…”
The oddity in The Plan is that it largely ignores 70% of the surface of the planet that’s not land: the oceans, or more specifically the blue carbon in them. For the first time, the capability of the oceans to rapidly draw down and permanently store vast quantities of CO2 was finally addressed at COP26.
New Zealand has an exclusive oceanic economic zone 14 times larger than our land area. Why isn’t the government (and heavy carbon polluters) using that incredible capacity to invest far more in locally produced blue carbon? Fed by the sun, with no need for irrigation or agricultural chemicals, some species can grow up to 1m/day, drawing down as much as five times more carbon dioxide from the atmosphere than rainforests, and permanently sequestering if not harvested and instead, cut and dropped into deep ocean.
Watch this (deep blue) space.
We need carbon. We need water, too. But like all good things, there can be too much. Too little water and we die of thirst. Too much, we drown. The same with carbon. Too little in the atmosphere in the form of carbon dioxide (CO2), we go into an Ice Age. Too much, the planet broils. We know this because of the geological evidence and from fundamental laws of physics and chemistry.
There is about 1.85 billion, billion tonnes of carbon on Earth. More than 99% is beneath our feet in soil and rocks including fossil fuels and permafrost. Just 0.2% or 43,500Gt is above the surface. Through natural processes, carbon is constantly in flux. That is, it’s moving between the land, the oceans, and living things (see ‘carbon cycle’ this website). When it’s burned, melted, or respired, it becomes a gas, combining with oxygen to make CO2. Some ends up in the atmosphere*. The rest is absorbed by terrestrial and oceanic ecosystems: forests, grasslands, wetlands, and marine animals and plants that make more than half the oxygen we breathe, and also as carbonic acid (H2CO3) dissolved in ocean and lake waters.
*Calculations at the bottom of this page.
It doesn’t take much CO2 in the atmosphere to warm the planet. Some 18,000 years ago, the concentration of CO2 was 189 ppm (parts per million). Global temperatures were 7-9°C cooler than today, and ice sheets several kilometres thick covered most of Europe and North America.
Over the next 10,000 years, the concentration increased 72ppm, to reach 261ppm. That was enough to warm the planet 6-8°C (Fig 2.).
*The average for 2021 will be about 417ppm because atmospheric concentrations change between summer (lower) and winter (higher); see the graph below for an explanation.
When governments signed the 2015 Paris Agreement they did so promising to keep global warming under 1.5°C by staying within a carbon budget. Each nation could choose how they would achieve this by reducing emissions—carbon ‘spending’—and increasing carbon ‘savings’ by planting carbon-absorbing trees. Obviously, to stay within the global budget, every nation had to play its part.
They didn’t. Emissions increased (Fig. 3)
And only if one-way climate tipping points, don’t tip.
“The drama here is that one characteristic of tipping points is that once you press the ‘on’ button you cannot stop it; it takes over. It’s too late. It’s not like you could say, ‘Oops, now I realize I didn’t want to melt the Greenland ice cap. Let’s back off.’ Then it’s too late.” – Johan Rockström, Breaking Boundaries: The Science of Our Planet (Video 1)
