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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...

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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)

Here’s a list of cause and effect relationships, showing that most climate change impacts will confer few or no benefits, but may do great harm at considerable cost.


While CO2 is essential for plant growth, all agriculture depends also on steady water supplies, and climate change is likely to disrupt those supplies through floods and droughts. It has been suggested that higher latitudes – Siberia, for example – may become productive due to global warming, but the soil in Arctic and bordering territories is very poor, and the amount of sunlight reaching the ground in summer will not change because it is governed by the tilt of the earth. Agriculture can also be disrupted by wildfires and changes in seasonal periodicity, which is already taking place, and changes to grasslands and water supplies could 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 the tropics or sub-Sahara, for example.


Warmer winters would mean fewer deaths, particularly among vulnerable groups like the aged. However, the same groups are also vulnerable to additional heat, and deaths attributable to heatwaves are expected to be approximately five times as great as winter deaths prevented. It is widely believed that warmer climes will encourage migration of disease-bearing insects like mosquitoes and 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 confer some commercial benefits, these are considerably outweighed by the negatives. Detrimental effects include loss of polar bear habitat and increased mobile ice hazards to shipping. The loss of ice albedo (the reflection of heat), causing the ocean to absorb more heat, is also a positive feedback; the warming waters increase glacier and Greenland ice cap melt, as well as raising the temperature of Arctic tundra, which then releases methane, a very potent greenhouse gas (methane is also released from the sea-bed, where it is trapped in ice-crystals called clathrates). Melting of the Antarctic ice shelves is predicted to add further to sea-level rise with no benefits accruing.

Ocean Acidification

A cause for considerable concern, there appear to be no benefits to the change in pH of the oceans. This process is caused by additional CO2 being absorbed in the water, and may have severe destabilising effects on the entire oceanic food-chain.

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.

Sea Level Rise

Many parts of the world are low-lying and will be severely affected by modest sea rises. Rice paddies are being inundated with salt water, which destroys the crops. Seawater is contaminating rivers as it mixes with fresh water further upstream, and aquifers are becoming polluted. Given that the IPCC did not include melt-water from the Greenland and Antarctic ice-caps due to uncertainties at that time, estimates of sea-level rise are feared to considerably underestimate the scale of the problem. There are no proposed benefits to sea-level rise.


Positive effects of climate change may include greener rainforests and enhanced plant growth in the Amazon, increased vegitation in northern latitudes and possible increases in plankton biomass in some parts of the ocean. Negative responses may include further growth of oxygen poor ocean zones, contamination or exhaustion of fresh water, increased incidence of natural fires, extensive vegetation die-off due to droughts, increased risk of coral extinction, decline in global photoplankton, changes in migration patterns of birds and animals, changes in seasonal periodicity, disruption to food chains and species loss.


The economic impacts of climate change may be catastrophic, while there have been very few benefits projected at all. The Stern report made clear the overall pattern of economic distress, and while the specific numbers may be contested, the costs of climate change were far in excess of the costs of preventing it. Certain scenarios projected in the IPCC AR4 report would witness massive migration as low-lying countries were flooded. Disruptions to global trade, transport, energy supplies and labour markets, banking and finance, investment and insurance, would all wreak havoc on the stability of both developed and developing nations. Markets would endure increased volatility and institutional investors such as pension funds and insurance companies would experience considerable difficulty.

Developing countries, some of which are already embroiled in military conflict, may be drawn into larger and more protracted disputes over water, energy supplies or food, all of which may disrupt economic growth at a time when developing countries are beset by more egregious manifestations of climate change. It is widely accepted that the detrimental effects of climate change will be visited largely on the countries least equipped to adapt, socially or economically.

Basic rebuttal written by GPWayne

Update July 2015:

Here is a related lecture-video from Denial101x - Making Sense of Climate Science Denial


Last updated on 5 July 2015 by pattimer. View Archives

Printable Version  |  Offline PDF Version  |  Link to this page

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Related Arguments

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


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Comments 326 to 350 out of 405:

  1. Moderators - At this point, given the large number of recent posts on this thread circling around a single sub-issue, a side-track, raised by (but really, IMO, not supported by) a single poster, perhaps it's time to invoke the Comment Policy stating: "Comments should avoid excessive repetition"?
    Response: [DB] Agreed. That also constitutes sloganeering/PRATT.
  2. All that and still no answer to Dikran's question
    So please answer this question directly and unambiguously: Is there anyone other than yourself that is promoting this hypothesis, yes or no?
  3. AH1's style is strangely reminiscent of that of Damorbel's and a few others who cluttered the 2nd law's thread with endless repetition of grotesque nonsense and self contradictions. KR's suggestion is appropriate.
  4. This could be the "acceptance of AGW" tipping point for people in the US: drought-related bacon shortage predicted.
  5. A thousand years ago climate is warmer than today. But we can not see in that period any traces of the predicted apocalypse connected to warming. It means that in calculations and models of climatologists is lurking fundamental err.

    [DB] Please familiarize yourself with this site's Comments Policy; additionally, please read the Big Picture post.

    Finally, commenting at Skeptical Science works best if you first limit the scope of your comment to that of the thread on which you post your comment and then follow up on those threads to see what respondents have said in response to you. There are quite literally thousands of threads here at SkS; if you do not engage with the intent to enter into a dialogue to discuss the OPs of the threads on which you place comments, you invite moderation of your comments.

    Note that your first statement is an unsupported assertion. When making assertions counter to that which is the understood state of the science, it is customary here to then also furnish a link to a reputable source which supports your assertion.

  6. setit-bagain: Assuming your comment survives moderation (it may not as it appears to be little more than baseless sloganeering) the simple fact is that your claim is unequivocally false. See here, or of course the IPCC AR4 (Working Group 1, §6.6) for summaries of the evidence. In addition, please substantiate your claims, with reference to the peer-reviewed literature that (a) there is a predicted apocalypse widely accepted among climate scientists, and (b) that even if this prediction is accepted, that it is false. Finally, your claim is, in and of itself, quite vague, so for a productive discussion please come up with a list of specific "fundamental errors" you feel exist, with substantiation in the literature to support your claims, and bring them up on the pertinent threads.
  7. And a further addition in addition to falseness - during HCO global temperatures were quite possibly warmer than today and definitely warmer in parts of the globe. However the transition to warm and cold was very slow compared to today's rate of change. Rate of change is what matter, not the absolute temperature.
  8. setit-bagain doesn't appear to be down with that whole "read the body of literature" thing. My life would be much happier if I never had to see that goofy Harris & Mann chart-picture-thing again.
  9. Having occasionally lurked for some time on SkS, I have a longstanding question for anyone who like to take a crack at it. I'd like to be able to offer to some of my skeptical friends and family an example of how AGW might be falsified. Let's say I'm conversing with a skeptic who (perhaps grudgingly) admits the reality of modest AGW but who considers it nothing to fret over, and certainly nothing to justify government intervention. Is there some precise, quantifiable outcome I can predict will obtain within 20 years from now if C02 remains above 400 ppm (or 450 or 500 or whatever), such that if it doesn't happen, I would have to concede I was mistaken as a "warmist"? Something along the lines of Haldane's famous rabbit in the Cambrian? Something I could place money on and collect in 2033?

    For example, could I say, if C02 remains above 400 ppm, then if by 2033 the global sea level average hasn't risen by at least 6 inches (or whatever) or the surface area of the Maldives has not been reduced by 10% (or whatever) or the Antarctic has not lost more than 5% (or whatever) of its ice volume or some other precise costly catastrophe does not occur before then, then we warmists were all mistaken?

  10. @KenD 50 years of cooling whilst atmospheric CO2 continues to rise, without evidence of substantial changes in the other forcings would constitute a pretty sound falsification I would have thought.  The good thing is that many climate models are available in the public domain, so at least the models are easily falsifiable by plugging in the observed forcings and seeing if the models can explain the observed climate.

  11. Sure, KenD.  

    1. Arctic sea ice will be effectively (<250k km2 area) gone in ten years at summer minimum.  According to Funder et al. (2011), Arctic sea ice extent hasn't been lower than current in about 8000 years.  The trend is currently greater-than-linear, and the linear trend has it effectively disappearing at summer minimum within eight years, about 70 years ahead of IPCC AR4 projections.  Even if we remain stable at 400ppm, sea ice is going to continue to decline thanks to the oceans continuing to move toward their equilibrium climate response to the stabilized forcing.

    2. Antarctic and Greenland land ice loss will continue over the next decade at least at the current rate found in Shepherd et al. (2013).

    3. Within fifty years, the process of ecological deconstruction or dis-integration will be obvious.  Species that can move rapidly will leave their niches and attempt to establish equilibria within environments.more suitable to their current configurations.  That may leave some slower and more interdependent species in the lurch.  Species may also respond genetically.  Then there are species that are up against the wall.  A wide range of studies, if academia is alive and well, should be reporting this type of significant change in the biosphere (already occurring, actually). 

  12. In other words, KenD, you don't have to wait for 2033.  You can win that bet right now.

  13. KenD,

    20 years is too short of a time frame, and making any one (or three) specific projections is dicey.  We're running a one-time experiment that has never happened in the past 100 million years... if ever.  There is no solid way to predict exactly what will happen when.  We know that bad things are going to start to happen now, but even then, no one will be able to connect the dots and unequivocally say "this is due to climate change."

    But things will get progressively worse.  The day will come in ten, twenty, or thirty years (maybe more, but I don't think so) when so many different things are happening and changing that the costs will be horrendous.

    With that said, whenever that day comes... there will still be more warming in the pipeline.  Climate change takes time, even though we have accelerated the process by a factor of 100.  So when the day comes that (if you could pick the right variables) you win your bet, it will already be way, way too late to do anything about it.  The genie will be out of the bottle. And things will continue to get worse from there.

    My favorite analogy for his is the man who jumped off of the roof of a skyscraper, and whenever he passed an open window, he was heard to say "So far, so good."

    But, to return to your question: no, I don't think so. There is no one particular parcel of evidence that you can reliably pick now, especially in a time frame as short as 20 years.

  14. Thanks for your helpful responses, DSL, Sphaerica, and Dikran. I'll see if one of my friends is willing to make a wager on the following, assuming we stay at or above current C02 levels (just shy of 400 ppm):

    If total ice sheet loss over the next 10 years is less than 3.44 trillion tons (344 billion tons times 10 years), then he wins and I lose.

    If Arctic sea ice is > 250k km2 area in 2023 at summer minimum, then he wins and I lose.

    The friend I'm thinking of is a fan of WattsUpWithThat, so I'm hopeful he'd be willing to bet on the above. I'm assuming these are pretty safe bets on my part?

  15. KenD:

    Instead of looking at the next 20 years, why don't you dig up some predictions made in the past - e.g., Arrhenius in 1896 - that have come true?

  16. KenD.

    Bet on volume rather than area, and you will almost certainly have money in the bank.

    And sadly, Sphaerica is correct about time spans and realisations.  The only slight point at which I would diverge is that I suspect that the genie's already been out of the bottle for a few years.

  17. Thanks, Bob and Bernard. Bob, I looked through some of the Arrhenius article, but I confess I'm not technical enough to home in on the best example of a prediction he made that has since come true. Bernard, if you were to place a bet on the minimum volume of Artic sea ice by 2023 (assuming C02 levels remain at or above current levels), what value you would bet on, assuming you want to keep your money safe?

  18. The economic impacts of climate change may be catastrophic, while there have been very few benefits projected at all.

    What about Figure 1 of this paper?

  19. Oops. I forgot to include the link:

    The Economic Effects of Climate Change

  20. Mark @344 - first off, almost all of the estimates in the Tol paper you reference are from the most conservative economists doing climate research (Nordhaus, Tol, Mendelsohn, etc.), so the paper almost certainly underestimates the economic damage from climate change (probably by a very large amount, in my opinion).  It's really interesting that it references Chris Hope, who now says that the social cost of carbon is in the ballpark of $150 per tonne of CO2, which is 1-2 orders of magnitude higher than Tol believes.

    Despite these underestimates, the paper still concludes that the net impact on GDP at 2.5°C will be negative, and we're already committed to about 1.5°C warming and still rising fast.  So I'm not really sure what your point is.

  21. Mark @344 - first off, almost all of the estimates in the Tol paper you reference are from the most conservative economists doing climate research (Nordhaus, Tol, Mendelsohn, etc.),

    Richard Tol is a conservative? That might be news to him! But OK...what do the "non-conservative" ("liberal?") economists say?

    Despite these underestimates, the paper still concludes that the net impact on GDP at 2.5°C will be negative, and we're already committed to about 1.5°C warming and still rising fast. So I'm not really sure what your point is.

    My point is that global surface temperature is rising by about 0.15 degrees Celsius per decade. So 2.5 degrees Celsius isn't likely to happen even in this century.

    In fact, per that paper, 1 degree Celsius warming from the present value was the peak of the positive effect on GDP. At 0.15 degrees Celsius per decade, that's more than 60 years in the future.

  22. Mark Bahner @ 346:

    1. What date is the 'present' you refer to in your assertion "1 degree Celsius warming from the present value was the peak of the positive effect on GDP"?
    2. What is good about knowing this will roll over us in 60 years, if the argument is used to delay taking action?
  23. New NASA study accepted by Geophysical Research Letters (Lau et al.) quantifies that wet places will get wetter and dry places will get drier--more floods and drought.  Heavy rain will increase, light rain will increase slightly, but moderate rain will decrease and no rain will be more frequent.  There is a summary with video of global map of changes.

  24. I'm not sure where to post this inquiry, and this thread seems the best, so it'll go here.

    I posted a link, a couple of weeks ago now, to a paper shared by Skeptical Science's Facebook page, onto my own feed.

    This resulted in an intense discussion with a pseudo-skeptic. Naturally, it had nothing particularly to do with the paper. Among the various arguments was one I have not encountered before, which was made in reply to a point I made about the problems related to the rate of current change:

    Your whole augment then is based not on the actual level of CO2 or temperature but that you can determine what the gradient of CO2 has been over the last 200 million years. Basic multivariable calculus just because you have a large change in the first derivative based on on variable doesn't mean that variable will dominate the function's value and to make that conclusion in any branch of science or engineering is prima facie false. Your system could simply be going through some oscillation before reaching a new steady state.

    I didn't pick up on the obvious misrepresentation ("Your whole augment then is based not on the actual level of CO2 or temperature but that you can determine what the gradient of CO2 has been over the last 200 million years") at the time.

    Anyway, my university calculus is, charitably put, rusty, so while I strongly suspect this claim is a load of bollocks (the notion that vast swathes of experimentally-verified atmospheric physics can be upended by basic multivariable calculus strikes me as ridiculous in the extreme) I'm not in a position to make a strong rebuttal (I did note that, indeed, trying to appeal to a principle of maths as a way of evading the evidence is bunk).

    Are there any other suggestions for rebutting this claim?

  25. Our current CO2 emissions rate is ten times faster than the rate which preceded the end-Permian extinction, 250 million years ago. Also, I've pointed out that fossilized leaves from the PETM confirm that a rapid CO2 increase (still not as fast as today's) stresses ecosystems.

    Scientists use more evidence than just first year calculus to determine climate sensitivity to CO2. Here's a figure from Royer et al. 2007 (PDF) which concludes that “a climate sensitivity greater than 1.5°C has probably been a robust feature of the Earth’s climate system over the past 420 million years”.

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