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Humans are pushing the Earth closer to a climate cliff

Posted on 15 August 2018 by John Abraham

A new paper, just published in the Proceedings of the National Academy of Sciences has received a lot of media attention. The attention is justified because the paper paints a very grim picture of the climate and what humans may be doing to it. In particular, the authors of this study tried to determine the trajectory that the Earth is on so we can predict what the future climate will be.

There are many really important insights from this paper. The authors wanted to know how feedbacks in the Earth’s climate will play a role in shaping the climate in the future. By feedbacks, we mean a change in one part of the climate that then causes another change, which in turn may cause another change, and so on, potentially setting up chain reactions.

Feedbacks are really important because they are changes that the natural system makes without being caused directly by humans.

For example, melting ice is one feedback, particularly in the Arctic. Humans have emitted greenhouse gases that have caused the Earth to warm. As the Earth warms, ice melts; as ice melts, it means there is less white reflective cover on the Earth surface. In fact, a lot of this ice melting is happening in the Arctic. Instead of having a white surface that reflects sunlight, we have open ocean water that absorbs sunlight. Consequently, melting of ice leads to more absorbed sunlight which then leads to more melting of ice – a reinforcing cycle, as illustrated below.


 Melting ice positive feedback cycle diagram. Illustration: John Abraham

Activating one of these cycles is bad news for a few reasons. First, it takes away a lot of control of the Earth’s climate from us. Right now, humans control the climate through our emissions of greenhouse gases. But once these cycles get activated, the Earth’s climate will partially control itself. That means it will be harder to stop the warming process.

The second reason this is bad news is that many of the cycles are linked together. For instance, the feedback cycle shown above might be strong enough to activate another cycle (for example, melting of permafrost and release of trapped methane). So, you can’t look at these feedbacks in isolation. You have to consider how they behave as a group.

The image below is taken from the paper. It shows 15 different feedback cycles. They are colored by the temperature at which they will be triggered. For instance, the authors believe the Greenland ice sheet will be activated when temperatures rise 1–3°C. The East Antarctic ice sheet however, shown at the bottom, will be activated once temperatures rise by 5°C or more. 

The various feedbacks also have connecting arrows to show how they are interrelated. For instance, there is an arrow connecting the Greenland Ice Sheet and Arctic summer sea ice. This means the two feedbacks affect each other.


 Map of potential tipping cascades. Illustration: Steffen et al. 2018, Proceedings of the National Academy of Sciences

This image is really important for understanding why scientists are so worried. Consider the summer Arctic sea ice. We know that it has decreased by about 70% in volume and perhaps 50% or so in area. Loss of Arctic sea ice will affect the Greenland Ice Sheet. That in turn will affect the West Antarctic Ice Sheet.

It doesn’t stop there;

Click here to read the rest

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Comments 1 to 17:

  1. The multiple tipping point  scenarios should have anyone worried, however the good news is the time frames in the study suggest theres still much to be gained by keeping emissions under 2 degrees. I get tired of the doom mongers claiming it's too late to do anything.

    However a study shows Antarcticas eastern glaciers are melting as well as the western glaciers, so are probably on the way towards a tipping point.

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  2. Through fossil CO2 emissions, people have driven a water vapor increase that triples the warming effect of the CO2 alone.   This should have served up an early warning that Earth's mysterious feedbacks won't magically resolve themselves in our favor, as we unnecessarily party our way through uncharted waters.

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  3. With several nonlinear positive feedback loops potentially adding to global warming its going to be very difficult to predict the extent of warming we will see, or the size of any rise in sea level over the next 80 years. All the more reason for us to limit the amount of CO2 that we release into the atmosphere.

    It's not really a case of it being too late to do anything, as if we stopped CO2 output now it would have a sigificant effect on curtailing the amount of warming we will see. Given the human race's ability to obfuscate about our addiction to the fossil fuel drug that we have, it's more a case of us being unwilling to tackle the problem and to meaningfully reduce our CO2 output in the time we have before the positive feedback loops kick in.

    Reducing CO2 levels to the degree that we need to means that we will have to change our economic models from expansionist to steady-state Herman_Daly_thinkpiece. Something I don't think that politicians in most countries have the will to do yet alone the ability to achieve. 

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  4. Reducing CO2 levels does mean we need to change our economic model towards steady state. Or at the very least we need to develop a system that grows in sustainable ways, and perhaps in the services sector,  rather than being based purely on maximising resource extraction until nothing is left.

    I think a steady state economy is inevitable sooner or later anyway. Take a look at gdp growth trends here and notice the falling trend over the last 40 years in developed countries, despite multiple tax cuts, a huge expansion of the money suppy, quantitiave easing, low interest rates, and endless stimulatory policies. I think anyone who believes high rates of gdp growth are possible in western countries anymore is delusional or will only achieve them very short term, and at the cost of huge debt levels and massive environmental damage.

    Developing countries are a different story. They have room to expand because of market demand for basic essentials of life. But they will reach a plateau eventually like western countries.

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  5. nigelj @1.

    I agree, there is a lot of reason to be concerned but this should motivate us not immoblize us.

    There are constant technological developments that give us options that didn't exist previously.

    Battery technology is rapidly maturing and with things like large scale redox flow batteries and solid state lithium metal batteries we can now plan electrical grids based almost entirely on intermittant sources of energy like wind and solar and can begin a phased movement to a transportation model based on electic power from those low carbon renewables.

    Three battery types in large scale grid storage


    Solid state lithium metal battery

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  6. An important quotes from the full Guardian article: 

    "the time frames in the study suggest theres still much to be gained by keeping emissions under 2 degrees"

    "we don’t know how long they will take to tip"

    "it is far too late to avoid all climate change – it is already here.

    What we are hoping for now is enough wisdom and will to at least stop short of going off these cliffs"

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  7. wili@6: "What we are hoping for... is enough wisdom... to... stop short of going off these cliffs"  Jesus, friend.  Consider the words you just wrote.  'Enough wisdom' should have already stopped us well short of those cliffs.  Nope, not an alarmist, we'll muddle through.  But Earth's biodiversity is well and truly f000ed, and we should grant ourselves the right to say so.  We need to call out the fact that MAGA comes at a cost: the wholesale screwing of any part of this globe that isn't covered in MAGA.  No, if you're out there in the 'great unknown', you're not MAGA, you're a waste dump, as Turkey just found out.

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  8. If you're going to run into a brick wall and there's nothing you can do to prevent that, you need to prepare for the crash while applying the brakes. No matter when you apply the brakes the outcome will be better. But it does not mean you can avoid crashing.

    CO2 concentrations are accelerating upwards, not just going up. We can talk mightily about staying below 2C, but when we see that we are going over, it's time to prepare for what comes next, while we keep putting on the brakes.

    The problem is that our foot is still on the accelerator.

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  9. ubrew12 @7: Wili's last quote from the OP:

    "What we are hoping for now is enough wisdom and will to at least stop short of going off these cliffs."

    You excluded "...and will" from your comment. Wisdom coupled with a will to act on it is absolutely necessary in mitigating and adapting to man-made climate change.

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  10. The diagrams are illustrative and the part about ice or snow surface reflecting heat could be at an interesting juncture.

    The snow and ice cover for the Northern Hemisphere is published often. (I wish it was every day). Last year, the cover was above the high-side of the standard deviation band through the melt season of August and September. It remained above into October. And then for this year it was above begining in April. This begins the window of maximum energy being received at the Earth's surface. And the reflecting surface was greater than the year before.

    So far into this August, it has remained above the deviation band.

    While two seasons in a row does not constitute a trend, it represents a possible change. Particularly, with the Danish Met Institute's chart of temps "North of 80", which has been below the mean line through this melt season.

    Typically, this one gets below freezing at around the third week in August. And then when it is night all day there is little energy to reflect back into space.

    Over the two seasons, this is encouraging.

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  11. Bob Hoye @10, increasing snow and ice cover over two years is not a trend, or even change as such in any fundamental sense. It is weather and normal short term cyclical variation. Any increase in ice less than 10 years in duration can be dismissed as temporary natural variation. Read the IPCC reports.

    Remember the so called pause? The denialists were telling us the "warming trend" was over, this was "change", the models were wrong, an ice age was immenent. No I said, its natural variation and it will not last. It came to an end abruptly over the last 4 years in dramatic fashion. 

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  12. While we continue to warm the atmosphere with CO2 emissions melting ice will continue. Basic physics. It may bounce around a bit from year to year but that is all.

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  13. Bob Hoye @10

    We are not in a cooling trend in North America, globally we are in a warming state of climatic transition which results in a disruption of local weather patterns.

    You just have to look at the amount of heat that is constantly being added to the Earth's surface through the mechanism of radiative forcing from things like the massive emission of carbon dioxide by human activity.

    Fortunately we have a meter for that located on this very page.

    2.646 billion atomic bomb quivalent heat units have been added to the Earth since 1998 alone. Most of that absobed by the oceans in a band 30 degrees on both sides of the equator. A place where ice and snow cover is not growing.

    Here in BC ice and snow cover is also not growing we are witnessing a rapid loss of alpine glaciers in British Columbia.

    Near total loss of glacial ice expected in BC, Alberta by 2100


    We did have greater than average snowfall here last winter resulting in much deeper snow packs. But this is duirng the winter months when insolation is at its minimum here. Snow falls here later in the year and melts sooner. 

    Resulting in a greater and greater occurance of catastrophic flooding.

    Record flooding in southern BC


    I see nothing to be encouraged about by the highly chaotic weather conditions we are being subjected to here in western NA or the increainsly catastrophics impacts of fossil fuel generated climate change.

    The Earth is not cooling based on almost all the evidence, it is warming at a rate that is overwhelming most natural mechanisms to adjust in a way that will mitigate catastrophic impacts like the loss of coral reef systems.

    Personally I have rarely seen the Sun in the last month and am glad that the large wildfire 3 kilometers to the north of my home has been put out. But much of this province is on fire with huge wildfire complexes that are joining together into incredible firestorms that cannot be fought. The same is happening right now in California. The smoke from BC reaches halfway across the continent and is causing unhealthy air conditions as far away as Manitoba.

    BC smoke blankets Southern Manitoba


    "Smoke from more than 500 wildfires burning in British Columbia has reached Manitoba prompting Environment and Climate Change Canada and Manitoba Health to issue a special air quality statement for the southern part of the province."

    Far from being encouraged, for many of us the experience is of being part of a very large scale and long term disaster movie where the conditions become increasingly hostile.

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  14. Bob, if you want a closer statistical look at NA snow, try here and especially here. Note especially spring and summer trends. Couple of things to think about it. As the earth warms, the atmosphere holds more water. If the warm air goes somewhere cool (up, towards poles etc), then it rains or snows. If it is cold enough to snow, then likely snow volume will increase. Come spring, (which is happening earlier), then you have snow cover influenced by two constrasting factors - more than usual amounts of snow to melt against warmer than usual temperatures to do the melting. Extent of snow cover does affect albedo, but the climatic effect is not much in winter (especially in high latitudes) because duh, there isnt much sun. Snow persisting through summer is much more important. Indeed the transition to an ice age happens when orbital wobbles result in cold summers at 65N and a persistance of snow. Right now, we are having very hot summers not cold ones.

    Looking a real trends in NH snow cover (see here), I dont see anything encouraging at all. It is downward. Nor is there is anything unusual historically about two years of increasing snow cover.

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  15. nigelj @ 4

    I firmly believe that we are already living far past what is sustainable for the environment over the long term.  We are consuming the world's resources far faster than is sustainable. Moving to adopting a steady-state economic model is imperative if we are ever to adapt to the restrictions that climate change and the enviroment as a whole imparts upon us.

    Will we be able to act in time and reduce CO2 sufficiently? I very much doubt it. Our brains and our sociities are just not set up right to make the logical deductions to arrive at the solutions we need to reach. I don't want to be a party pooper, but that's just the way I see it.

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  16. nigelj @ 4

    Reducing CO2 levels does mean we need to change our economic model towards steady state. Or at the very least we need to develop a system that grows in sustainable ways, and perhaps in the services sector, rather than being based purely on maximising resource extraction until nothing is left.

    I agree that the global economy is up against multiple planetary boundaries, and must eventually become steady-state. AFAICT though, the specific problem of anthropogenic global warming is comparatively easy: we 'merely' need to replace fossil carbon with carbon-neutral energy sources. That's already underway, driven to an extent by market forces in response to piecemeal government regulations and subsidies to promote 'alternative' energy. Collective intervention on larger scales is needed to accelerate the transition, by internalizing more of the marginal climate change costs in global prices for fossil carbon. It's not that radical an idea. YMMV, but I've made no secret of my support for a US revenue-neutral Carbon Fee and Dividend with Border Adjustment Tariff.

    Once transferring fossil carbon to the climatically-active pool is no longer cost-effective, we'll have bought time to work on all the other problems.

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  17. Mal Adapted @16, agreed carbon fee and dividend has to be the central policy for all the reasons you have given eloquently and in detail here and over at RC. (Sad that you know who doesn't get it). And Michael Mann also thinks a carbon fee is a potential solution.

    Although we probably have to solve various environmental problems in parallel, and they tend to mutually help each other in many cases.

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