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All IPCC definitions taken from Climate Change 2007: The Physical Science Basis. Working Group I Contribution to the Fourth Assessment Report of the Intergovernmental Panel on Climate Change, Annex I, Glossary, pp. 941-954. Cambridge University Press.

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Positives and negatives of global warming

What the science says...

Select a level... Basic Intermediate Advanced

Negative impacts of global warming on agriculture, health & environment far outweigh any positives.

Climate Myth...

It's not bad

"By the way, if you’re going to vote for something, vote for warming. Less deaths due to cold, regions more habitable, larger crops, longer growing season. That’s good. Warming helps the poor." (John MacArthur)

At a glance

“It's not going to be too bad”, some people optimistically say. Too right. It's going to be worse than that. There are various forms this argument takes. For example, some like to point out that carbon dioxide (CO2) is plant-food – as if nobody else knew that. It is, but it's just one of a number of essential nutrients such as water and minerals. To be healthy, plants require them all.

We know how climate change disrupts agriculture through more intense droughts, raging floods or soil degradation – we've either experienced these phenomena ourselves or seen them on TV news reports. Where droughts intensify and/or become more prolonged, the very viability of agriculture becomes compromised. You can have all the CO2 in the world but without their water and minerals, the plants will die just the same.

At the same time, increased warming is adversely affecting countries where conditions are already close to the limit beyond which yields reduce or crops entirely fail. Parts of sub-Saharan Africa fall into this category. Elsewhere, many millions of people – about one-sixth of the world’s population - rely on fresh water supplied yearly by mountain glaciers through their natural melt and regrowth cycles. Those water supplies are at risk of failure as the glaciers retreat. Everywhere you look, climate change loads the dice with problems, both now and in the future.

Please use this form to provide feedback about this new "At a glance" section. Read a more technical version below or dig deeper via the tabs above!

Further details

Most climate change impacts will confer few or no benefits, but may do great harm at considerable costs. We'll look at the picture, sector by sector below figure 1.

IPCC AR6 WGII Chapter 16 Figure FAQ 16.5.1

Figure 1: Simplified presentation of the five Reasons for Concern burning ember diagrams as assessed in IPCC AR6 Working Group 2 Chapter 16 (adapted from Figure 16.15, Figure FAQ 16.5.1).


While CO2 is essential for plant growth, that gas is just one thing they need in order to stay healthy. All agriculture also depends on steady water supplies and climate change is likely to disrupt those in places, both through soil-eroding floods and droughts.

It has been suggested that higher latitudes – Siberia, for example – may become productive due to global warming, but in reality it takes a considerable amount of time (centuries plus) for healthy soils to develop naturally. The soil in Arctic Siberia and nearby territories is generally very poor – peat underlain by permafrost in many places, on top of which sunlight is limited at such high latitudes. Or, as a veg-growing market gardening friend told us, “This whole idea of "we'll be growing grains on the tundra" is just spouted by idiots who haven't grown as much as a carrot in their life and therefore simply don't have a clue that we need intact ecosystems to produce our food.” So there are other reasons why widespread cultivation up there is going to be a tall order.

Agriculture can also be disrupted by wildfires and changes in the timing of the seasons, both of which are already taking place. Changes to grasslands and water supplies can impact grazing and welfare of domestic livestock. Increased warming may also have a greater effect on countries whose climate is already near or at a temperature limit over which yields reduce or crops fail – in parts of the Middle East and sub-Saharan Africa, for example.


Warmer winters would mean fewer deaths, particularly among vulnerable groups like the elderly. However, the very same groups are also highly vulnerable to heatwaves. On a warmer planet, excess deaths caused by heatwaves are expected to be approximately five times higher than winter deaths prevented.

In addition, it is widely understood that as warmer conditions spread polewards, that will also encourage the migration of disease-bearing insects like mosquitoes, ticks and so on. So long as they have habitat and agreeable temperatures to suit their requirements, they'll make themselves at home. Just as one example out of many, malaria is already appearing in places it hasn’t been seen before.

Polar Melting

While the opening of a year-round ice-free Arctic passage between the Atlantic and Pacific oceans would have some commercial benefits, these are considerably outweighed by the negatives. Detrimental effects include increased iceberg hazards to shipping and loss of ice albedo (the reflection of sunshine) due to melting sea-ice allowing the ocean to absorb more incoming solar radiation. The latter is a good example of a positive climate feedback. Ice melts away, waters absorb more energy and warming waters increase glacier melt around the coastlines of adjacent lands.

Warmer ocean water also raises the temperature of submerged Arctic permafrost, which then releases methane, a very potent greenhouse gas. The latter process has been observed occurring in the waters of the East Siberian Arctic Shelf and is poorly understood. At the other end of the planet, melting and break-up of the Antarctic ice shelves will speed up the land-glaciers they hold back, thereby adding significantly to sea-level rise.

Ocean Acidification

Acidity is measured by the pH scale (0 = highly acidic, 7 = neutral, 14 = highly alkaline). The lowering of ocean pH is a cause for considerable concern without any counter-benefits at all. This process is caused by additional CO2 being absorbed in the water. Why that's a problem is because critters that build their shells out of calcium carbonate, such as bivalves, snails and many others, may find that carbonate dissolving faster than they can make it. The impact that would have on the marine food-chain should be self-evident.

Melting Glaciers

The effects of glaciers melting are largely detrimental and some have already been mentioned. But a major impact would be that many millions of people (one-sixth of the world’s population) depend on fresh water supplied each year by the seasonal melt and regrowth cycles of glaciers. Melt them and those water supplies, vital not just for drinking but for agriculture, will fail.

Sea Level Rise

Many parts of the world are low-lying and will be severely affected even by modest sea level rises. Rice paddies are already becoming inundated with salt water, destroying the crops. Seawater is contaminating rivers as it mixes with fresh water further upstream, and aquifers are becoming saline. The viability of some coastal communities is already under discussion, since raised sea levels in combination with seasonal storms will lead to worse flooding as waves overtop more sea defences.


Positive effects of climate change may include greener rainforests and enhanced plant growth in the Amazon, increased vegetation in northern latitudes and possible increases in plankton biomass in some parts of the ocean.

Negative responses may include some or all of the following: further expansion of oxygen-poor ocean “dead zones”, contamination or exhaustion of fresh water supplies, increased incidence of natural fires and extensive vegetation die-off due to droughts. Increased risk of coral extinction, changes in migration patterns of birds and animals, changes in seasonal timing and disruption to food chains: all of these processes point towards widespread species loss.


Economic impacts of climate change are highly likely to be catastrophic, while there have been very few benefits projected at all. As long ago as 2006, the Stern Report made clear the overall pattern of economic distress and that prevention was far cheaper than adaptation.

Scenarios projected in IPCC reports have repeatedly warned of massive future migrations due to unprecedented disruptions to global agriculture, trade, transport, energy supplies, labour markets, banking and finance, investment and insurance. Such disturbances would wreak havoc on the stability of both developed and developing nations and they substantially increase the risk of future conflicts. Furthermore, it is widely accepted that the detrimental effects of climate change will be visited mostly on those countries least equipped to cope with it, socially or economically.

These and other areas of concern are covered in far more detail in the 36-page Summary for Policymakers from the IPCC AR6 Synthesis Report, released in March 2023. The report spells out in no uncertain terms the increasingly serious issues Mankind faces; the longer that meaningful action on climate is neglected, the greater the severity of impacts. The report is available for download here.


Last updated on 21 April 2023 by John Mason. View Archives

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Further reading

National Geographic have an informative article listing the various positives and negatives of global warming for Greenland.

Climate Wizard is an interactive tool that lets you examine projected temperature and precipitation changes for any part of the world.

A good overview of the impacts of ocean acidification is found in Ken Caldeira's What Corals are Dying to Tell Us About CO2 and Ocean Acidification

Denial101x video

Here is a related video lecture from Denial101x - Making senses of climate science denial


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Comments 151 to 175 out of 229:

  1. Joseph#150: Nice cherrypick! From the same (hardly scientific) article: “Since 2000, we’ve lost about 30 percent of the ice area as of 2009, but the thickness of at least the main glacier, the northern ice field, hasn’t changed a great deal. It was 50 meters thick then and now it’s on the order of 45 meters thick,” he said. Lack of long-term data concerning the thickness of the glaciers is what undermined their forecast, Hardy said. “Before 2000, we had no reference for how to treat the thinning other than by looking at historical photographs.”
  2. No cherry picking, as a matter of fact your posting goes to my point! When scientists don't have all the data or all the variables and they make forecasts based on that, then that disconnect is created. Again this is not to say that global warming is not happening, or is not melting Kilimanjaro's ice, it just says that maybe there is a disconnect between currents trends vs. projections.
  3. Joseph#152: By definition, a cherry pick is the use of a small subset of the available data, usually to draw a pre-conceived conclusion. This is only a 'disconnect' for people who keep score based on who said what when. Those who understand the comment made by Hardy can see that such a prediction is justifiably updated by more complete analysis. This is the normal process of science or for that matter any predictive endeavor. BTW, setting up a misrepresentation of another's argument so it can then be shown as a potential 'disconnect' is known as a strawman. In this case, 'they got the date the glacier would melt wrong' is a strawman. It is far more productive if we engage in substantial issues.
  4. For some credibility, please pick a prediction from AR4 that you think is overstated (ie something with reputable science behind it). Also, the statements about what is happening at this time are not full of doom & gloom. Furthermore 2 key ones (sealevel rise and arctic ice loss) show how conservative the predictions were. What are the indicators that you would choose, that if went bad would make you say "OMG - I've been an idiot"? The two for me (currently doing okay but expected to go bad) would be world mortality and global grain production. The problem is that by the time you see a bad 10 year trend in these, a lot of people would have suffered. You want to wait till the house is burning down?
  5. #150, 152 Joseph, we don't base our observations on a single glacier, see for example this post most glaciers worldwide are retreating and that trend is accelerating. Note John Cook's second-last sentence. A vast amount of information underpins the projections, and the tendency has been for the IPCC to err on the conservative side in their projections.
  6. Muoncounter#153 Every posting that rebutted mine that contained a single link to prove the poster's position was a cherrypick as well, but did anyone point that out? I didn't go to great lengths to find this article, it took me literally 1-2 minutes with a single google search to find this article. So it wasn't much of a cherrypick. So you are saying it is a strawman because the substantive issue in the prediction is the melting of the glacier not so much the time it takes to melt??? So global warming of 1 deg over a decade is the same as global warming of 1 deg over a century? Why shouldn't we keep score of the predictions as it relates to their timeline? And how is this not a substantive issue? I would say that us, (yes US!), AGW proponents have the obligations to keep score much less the willingness! I would have expected you to say something to the effect that, yes Hardy messed up, but if you took all the predictions as a whole then the number of studies who got it right vs. the ones who got it wrong is 10-1, or something to that effect. Then I would have expected you to give me a link showing this (I would love to see this, btw). That answer I would have respected, instead of brushing this off by this, "It is far more productive if we engage in substantial issues", i.e. "let's the change the subject" business. If anything this answer just reinforces any reader's belief in a disconnect between the predictions and the current trends
  7. Joseph#156: "wasn't much of a cherrypick." The point was this: You found a single example that showed you what you wanted to hear -- and you generalized it to 'there's a disconnect!' That's the 2nd part of the definition of cherrypick I cited. It is this logic that turns 'they got the weather wrong yesterday,' into 'they sure can't say anything about climate.' "global warming of 1 deg over a decade is the same as global warming of 1 deg over a century?" Your example was a glacier melting in a specific year vs another in the same decade or two. Please avoid these giant leaps from the small to the global. This is not 'the science of predictions,' which we usually call 'climastrology.' There are no crystal balls or tea leaves in climate work. This is difficult science, worked by serious folks who see their every word picked over by self-appointed, self-taught and self-righteous critics - who hardly ever have to answer for their own words. Instead, the scientists often have their own words turned against them. BTW, have you applied your prediction-tester to Bastardi's cooling forecast? To Watts on this year's minimum Arctic sea ice extent? If you want to keep a prediction scorecard, please be sure to check both sides of the fence. So yes, let's engage in more substantial issues. If you don't respect that, so be it. We'll let the readers decide on where the disconnect lies for themselves.
  8. Muoncounter, I thought the whole idea of this website WAS to debate these very issues, instead what I am hearing from you is that I shouldn't question anything you say because it is "difficult science" and it's not "climastrology", and who am I to question them (or maybe I should say, "you"), because after all I am just a "self-appointed, self-taught and self-righteous critic"?! You are correct in one assumption, I am not a scientist, but it is this website that invited debate from the general public (and aren't you a moderator on this site? you certainly act like it), but instead it seems to me more and more that criticism is not welcome on this site. And as an FYI, no I am not going to apply a prediction tester to the other side, simply because the other side is non-scientific, and therefore their predictions have no credibility to start with. I am out.

    [DB] "I thought the whole idea of this website WAS to debate these very issues"

    The goal of Skeptical Science is to explain what peer reviewed science has to say about global warming.  While this site does invite discussion of the science, to characterize that discussion as a "debate" is to lend false credence/false equivalency to much of what comes out of the anti-science portion of the blogosphere (and traditional mass media, mores the pity).

    Essentially, the basics of climate science and global warming are indeed "settled science"; what is being discussed in the literature today is how much warming we can expect, how fast we can expect it, and how bad things will get.

  9. Joseph, I simply objected to turning a thread that deals with a wide range of important topics (those bold paragraph headings in the original post) into a testing ground for various specific predictions. I don't know how you read that as 'I shouldn't question anything.' Nor did I apply the words 'self-appointed' etc to anyone in particular. As to your claim that 'criticism is not welcome,' nothing could be further from the truth. However, criticism of what one person said is vastly different from a critical discussion of ideas. FYI, applying a critical eye to one side certainly looks one-sided, but that's just my opinion. It is a shame that a call for a more substantial discussion should provoke such ire.
  10. Eric the Red @160, the only debate which matters for the science is that which occurs in the peer reviewed literature. You, just as much as any other denier, are quite welcome to put your arguments into publishable form. That you are unwilling or unable to do so is a clear indication that your view point is not worthy of consideration by working scientists, and therefore not worthy of attention on a website whose stated purpose is to expound the published science of climate change. That you choose to 'debate' on the web when you clearly disagree with much published science, IMO, shows that you are not trying to learn the truth. If you where you would be trying to become involved in the debate that matters. Rather you are trying to persuade those who are ill informed on the topic in the full knowledge that you will be unable to persuade those who are well informed.
  11. EtR. There is certainly a lot under debate in climate science, but the basics (Temp is increasing, CO2 is a greenhouse gas, CO2 is increasing, humans are responsible) are in fact "settled science." By that I mean that no one in the scientific community thinks these are interesting problems anymore. The evidence behind those propositions is just too compelling. It has been for decades now. Also, let's be honest. This forum does not constitute a true debate on the scientific matters. To be part of the real scientific debate, we would actually have to be doing original research and actively publishing that research in peer reviewed journals, not just posting to blogs on the web. To be part of the scientific debate requires that we be informed and capable enough to convince other well informed and capable people that we have something substantial to contribute. People feel annoyed by this state of affairs, I guess because they feel like decisions are being made that affect them without their having a say. Of course, they might feel more annoyed if they were actually forced to go through the training needed to allow them to participate in the scientific debate! More pertinently though, this resentment is misguided. The only decisions that are being within the scientific community are with respect to what the evidence says about how the world works and our place in it. What we actually do as a society will have to be a much more public decision because that involves taking values into account. Without scientfic evidence, you can't have rational decision making -- it becomes impossible to determine whether any action actually serves the values it is intended to serve.
  12. Hello, I'm a newcomer in this field. I have read most of the arguments on all sides. This site by the way is really good. Keep up the god work The point of my question here is - OK, AGW is real, but for policy and decision makers, how much confidence can be placed in IPCC predictions, and how much weight should we attach to them? [- inflammatory comment snipped-] It would be great if any replies could be objective, rather than emotive.
    Response: (Rob P) Please take heed of the advice in your last sentence. Make sure posts adhere to the comments policy. If you wish to re-frame your question this SkS post is the relevant thread to comment on: Is the IPCC alarmist?
  13. Lancelot. Follow the moderator's link. I've responded there.
  14. It seems bad for Tuvalu. The Economist, likening the situation to a "canary in a coal mine," reports that Tuvalu is both running out of fresh water and beginning to suffer from sea level rise.
  15. I have visited Tuvalu. The situation there is terrible. They had a very traditional lifestyle and are really friendly people. I still have two grass hula skirts they gave me. The people there have few options besides migration. Your link says that Australia turned down a Tuvaluan proposal for migration. Who will take them in? Increased waves from stronger storms (caused by AGW) have combined with sea level rise to poison most of their fresh water. Your link says Samoa is also rationing water. Samoa is a much larger country with much greater land mass. It must be a serious drought for Samoa to be running short of water.
  16. Regarding the entries about western tree mortality, pine beetles under the Environment negatives in the Intermediate tab, I quote from a blog post by a fellow I've known for more than forty years. This is not peer-reviewed science, but I think it reflects a human perspective on those environmental negatives (the ellipses in the post are his, and I have omitted nothing): "I got lost in the details of travel and the hassle of finding places to work on the blog/sort pictures and talk about the travels. The massive environmental upheaval caused by global warming in the pine and spruce forest of Idaho and Montana is stunning. The forest is dieing. Pine Beetle and Spruce Moths are unchecked by the long frosts of winter. The result is hundreds perhaps thousands square miles of dead and dieing forests. There is the loss of the wood and timber...the water holding of the trees, the air purification, the oxygen generation but, more.... The millions of pine and spruce needles in the waters have changed the PH of the lakes and streams. The water born insect life is gone. Three different streams, three hoops set out for three days each ... less than 20 insects collected where there should have been thousands. Breeding salmon seen but no fry, no first or second year fish, no trout, no white fish, no suckers...the streams are dead. "Sorry my mind is still struggling with the facts and unsure as to how I will deal with those who say my truth is lies. Will they come walk the streams, roll the rocks, hang the hoops, count the insects, float the rivers and prove me wrong or will they simply move their mouths in denial? I was unable to write this last summer and do not know what I can do this year."
  17. Article on China's program to modify weather

    "As extreme weather events such as drought and flooding become more common, protecting the nation's main wheat producing areas grows in urgency - thus the first regional program chose the northeastern parts of the country,..."

  18. Under "Sea Level Rise" it would be good to specifically mention coastal erosion. Rising sea level threatens not just those who will find themselves beneath the waves, it also threatens those atop the tall cliffs. Basically rising sea level changes the mass balance of sediment on beaches. By creating new room ("accommodation space") for sediment storage, sea level rise can quickly drain a beach of sediment, exposing the surface protected by the beach. Also it obviously provides more ready access for storm waves to the base of erosional bluffs. To better understand the messy nature of marine transgression during sea level rise, one could look to areas where subsidence has simulated this effect such as on the Mississippi delta (size warning - 2 mb pdf): I don't know of a nice paper that looks at cases like this and uses it as an analogy for climate-change related sea level rise.
  19. Edit: Debunked Saleska paper removed from the positive column - the Amazon did not green up during the exceptional 2005 drought - see:Samanta (2010) Nemani (2003) also excised. It does not imply enhanced forest growth with future global warming. A further reduction in cloud cover over the Amazon will lead to more warming of the forest canopy and, possibly, exceeding a heat tolerance threshold. See SkS post: Amazon Drought: Heat Stress Linked To Mass Tree Die Off In 2005 and 2010
  20. Interesting article, thanks for the mental meal! A couple of questions: I'm in Australia - will we get *fewer* droughts as a result of global warming? (Thanks for the video link @muoncounter, was awesome). It's kinda important, given we've got a carbon tax as the current political football. Also, can it be predicted *when* (ie which season) increases/decreases in rain will occur? The true nightmare in OZ is a wet spring followed by a hot summer, as that means insane bushfires. However a dry spring/wet summer is awesome. Makes a huge difference! - What about refugees? How many millions of people are going to have to move? That's going to create a huge cost, surely. - Finally...ok, this one's creepy, but I have to ask. If (i) it's true that most human genetic diversity is in Africa, and (ii) Africa gets it in the neck, are we going to lose great wodges of genes that could be used for treating inherited diseases etc? I don't mean to treat people as harvestable cattle, but if it is a genetic loss, and pointing out the loss can reduce the likelihood of them being left to die, then it needs to be said...
  21. I bet this has already been metioned, but what happens when the ice caps melt? Wouldn't high up northern places become habitable? How about the deserts , which will border the oceans, creating new forests for all. And most of all, wouldn't it be great for microorganisms (especially Archea) to live, therefore giving us new lifeforms that take the place of the old niche of the old lifeform
  22. ShadedX, the problem is that even if temperatures, say, in northern Canada or Siberia became suitable for growing wheat or whatever, or if it starts raining regularly in somewhere currently desertified (not generally forecast, but lets imagine for a moment)... you will not develop the soils required to sustain agriculture or forestry for many hundreds or more likely thousands of years. Soil development (pedogenesis) is a very slow process - a good example is the vegetation successions you see after ice retreat at the end of past glaciations - trees only thrive thousands of years after the first colonising grasses and shrubs.
  23. Reiterating skywatcher - its not whether warming is better or worse, but the rate at which change occurs. Rapid change (and this is very rapid change in geological terms) is associated with mass-extinctions. I doubt very much that humans would go extinct but the disruption to our agriculture will be very considerable. The question to ask is with the cost of mitigation is less than the cost of adaption. Studies so far say better to mitigate.
  24. Did anyone else cringe reading this one: === Melting Glaciers The effects of glaciers melting are largely detrimental, the principle impact being that many millions of people (one-sixth of the world’s population) depend on fresh water supplied each year by natural spring melt and regrowth cycles and those water supplies – drinking water, agriculture – may fail. === 1) One-sixth of the world's population is not just many millions but at least a billion. 2) While I could believe a billion people are dependent on rainwater runoff, or spring runoff from melting snow that fell during the winter, where exactly are there a billion people in the world depending on water from actual glaciers? If global warming was somehow able to stop rain, or prevent snow from falling every year, I could see that being a problem for a billion people or more. As far I know (though I'm admittedly quite ignorant on the subject) reduced global precipitation hasn't been proven as a result of AGW yet. Has it? This statement seems takes an easily observable phenomenon (glaciers shrinking) that the general public can understand, and associate it *incorrectly* with catastrophic results. It's this attitude of alarming the public with misleading claims that make me skeptical of AGW reporting accuracy in general.
  25. mohyla103, to find out more details, visit the Intermediate Version of this topic, have a look at the references used (Barnett 2005 and Immerzeel 2010), and then come back and state where you found the "misleading claims".

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