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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).

Agriculture

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.

Health

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.

Environmental

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

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

Comments

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Comments 26 to 50 out of 265:

  1. Vinny Burgoo at 07:35 AM on 13 March, 2010 "The whole field is less than scientifically kosher and large areas of it are politicised. " Mountains out of molehills, you illustrate my point nicely, thanks. What about dehydration is political, anyway? I don't understand that.
  2. Is warming good or bad? If it prevents an ice age it is good. In the ice age section it is said "we will not have an ice age because of the CO2 we have released." Well that may mean that in the future we do not get any warmer if the ice age mechanism continues and the CO2 effects cancel it out. So our greenhouse gases do good. If the ice age factors are at work. An ice age is not the only outcome, but the factors may be just as important as COP2. OK?
  3. There is a element of presentation that tends to mislead. I will give an example. There is only one benefit listed for human health, but several detriments. This obscures the fact that in net, warming is benefit to human health. I am not saying it is good for humans, I am saying that the higher temperatures themselves are a benefit. Where do people vacation? In Greenland, or in Crimea? Clearly, the temperatures themselves are not the problem.
    Response: I'm open to adding more benefits - if you find peer-reviewed papers that show benefits to health from global warming, please post them and I'll add them to the list.
  4. coloursoflife, do you really think that the behaviour during vacations is an appropiate indicator of the overall benefit of a climate over another? I could agree only if you let me stay on paid vacation 365 days a year :)
  5. Agriculture negatives- More CO2 produces lower protein levels in the plants, so a larger quantity is needed to provide the same amount of protein. "Despite the large body of research on the effect of elevated CO2 on primary productivity, few studies consider the overall nutritional value of plants." More CO2 also produces more cyanide in the plant, while at the same time lowering protein in the plant. Animal and human tolerance to cyanide is reduced by lower levels of protein. Coupled with reduced protein levels per plant, this makes plants more toxic. Paper "Changes in Nutritional Value of Cyanogenic Trifolium repens Grown at Elevated Atmospheric CO2" Overview of this research from Monash University Audio and transcript from ABC Science Show interview with Roslyn M. Gleadow
  6. PS Trifolium repens is clover, sort of an important crop
  7. A bit more from the summary at the end of the paper "Protein content of food crops such as wheat and rice are predicted to contain to 15–20% less protein by the end of this century (Taub et al. 2008)." "Insect studies have shown that animals compensate for the lower protein content of plants grown at elevated CO2 by eating more (Lincoln et al. 1993). If this is also true of grazing mammals, then they would ingest more cyanogenic glycosides along with the rest of the plants in mixed pastures." "...it is possible that pastures rich in T. repens could become unsuitable for livestock if atmospheric CO2 continues to increase."
  8. A bit far fetched maybe, but AGW is causing more space junk to threaten satellites and spacestations. The cooling of the stratosphere causes the atmosphere to contract which lowers the density of the upper atmosphere. This reduces drag on debris which therefore stays longer in orbit. http://www.newscientist.com/article/mg20627663.000-climate-change-is-leaving-us-with-extra-space-junk.html
  9. The link to the skeptic argument is broken.
  10. Hello all, Just to throw this into the mix... http://www.youtube.com/user/greenman3610#p/a/u/1/uE6at2IEUOU
  11. and this http://www.uoguelph.ca/news/2010/08/bbb.html
  12. and why not... http://www.youtube.com/user/greenman3610#p/a/u/2/g093lhtpEFo
  13. Re: Johngee (37) Dude, ya gotta warn people when posting a link to a video with Monckton testifying in from of Congress!!! You owe me a new keyboard. ;) Re: Johngee (36) Another game-changer; Caldeira has been predicting this for some time (don't have the links handy, but Lord Google Scholar finds much). Tropical forests will continue to be carbon sinks, but temperate & boreal forests transition to net carbon emitters with rising temps (multifactoral reasons). A suggestion: links to papers are appreciated, but it is customary (and just good form) to preface with a summary of understanding of what to expect. This goes double with videos with Monckton... Re: Johngee (35) See above comment about good form (and remember: always book good money on the T-Rex vs people). Make sure to watch the entire Alley CO2 Biggest Control Knob lecture. The Yooper
  14. All taken on board Dan. Watched the lecture. Very good indeed! I'd like to comment on Monckton/congress thing myself but everytime I try my voice gets lost in a scream of discombobulation.
  15. Re: Johngee (39) Welcome aboard. There's room for all here. At Real Climate, Climate Progress, Deep Climate, Rabett Run, Open Mind, Only In It For The Gold (the list of quality science blogs is very long). I lurked for about 18 months before I started chiming in. There's a ton of basal and ancillary background material to digest. If you're interested, go to Real Climate to the Start Here tab & find your comfort level. Any questions I can help with, just post. Welcome aboard. The Yooper
  16. 'Severe consequences for over 60 million people dependent on ice and snow melt for water supply (Barnett 2005, Immerzeel 2010)' It's good to see that you update things, JC, but now you've understated the problem. Immerzeel et al's 60 million is related to ice-melt alone (not ice and snow) and is for only five river basins. Adding the inhabitants of the Tarim oases in NW China might take the number that'll eventually be threatened with food insecurity because of vanished glaciers up to 70 million. (I've never found a reliable number for the western China component. Thanks to Barnett et al, many sources say that 23% of China's population - all in Western China - relies on glacial melt but that's hooey. I suspect the claim originated with a journalist's ambiguous padding of a 2004 newspaper interview with Yao Tandong.) Adding a quota for ex-Soviet Central Asia might take you to... 100 million? The small populations outside Asia... Dunno, but a wild guess: 150 million in all. Or you could stick with ice *and* snow melt and reinstate Barnett's (dodgy) 1 billion. But at the moment you're using a partial number for ice and ascribing it to ice and snow, which is no better than the earlier problem (Barnett's billion all down to ice).
    Response: Thanks for the feedback. I've gone for "at least 60 million people dependent on ice melt" which is as weak as dishwater but Immerzeel is really the best estimate we've got so far, even if it only covers 5 river basins. Where does your figure for NW China come from?
  17. JC: 'Where does your figure for NW China come from?' From a very, very rough estimate of the total population of the Tarim oases.
  18. This PNAS abstract shows decreasing rice yields under higher night time temperatures if you're looking for non greenhouse based work on (dis)advantages of higher CO2 on crop growth.
  19. The amount of debate an attention to minutiae is unbelievable on this site. It is good in a way but I am curious as to why the issues on this site evoke more discussion than almost anything else I can think of. The possible downsides to this arguing about AGW/climate change are that it overshadows other very important issues that affect people and planet. Other issues that are important irrespective of AGW are: Destruction of the rainforest which is needed for species diversity Our oceans are being overfished We use too much of the world's resources on average per person Species extinction Political apathy resulting in necessary change not happening quickly enough Also, if fossil fuels are running out, does this timing coincide nicely with the need to reduce the use of fossil fuels? Finally, I would love an assurance that the people on this site putting masses of effort into collating data and facts actually live in a sustainable way ie. you practice what you profess.
  20. hapivibe wrote : "Finally, I would love an assurance that the people on this site putting masses of effort into collating data and facts actually live in a sustainable way ie. you practice what you profess." Why ? Would you disregard the opinion or diagnosis of a doctor who smokes, especially if you were being told that your cancer was caused by smoking ? Or if you were told to give up smoking because it is badly affecting your health ?
  21. Witnessing myriad discussions focusing on whatever shreds of countervailing evidence are available as alternative explanations for what is at root a fairly simple, bulky and ultimately powerful process leaves me completely unsurprised that you find discussions here dominated by minutiae, hapivibe. Bloating the importance of little things by employing large rhetoric is the sharpest tool in the kit of people who for whatever reason wish to ignore the CO2 problem. You're absolutely right that we're imposing a heavy load on the systems we depend on. Getting a grip on the CO2 problem is a key part of not further exacerbating our failure to account for our impact on the planet. More, there's little reason to believe that solutions to the problems you mention are somehow mutually exclusive, rather it's probably reasonable to suggest that integrated approaches would be more beneficial. As you suggest, apathy is our enemy, an old human failing seemingly only overcome in moments of crisis. Looking at the various graphs of depressing facts, what's the largest contributor to fossil fuel GHG emissions? Coal is the most abundant and presently active feedstock for CO2. There's plenty of coal and we're burning more of it than ever. We're not going to run out of coal fast enough to rely on depletion of fossil fuels as a solution to CO2 emissions. There's no data so far indicating we're going to stop burning coal. Depletion as a solution to CO2 emissions on the timescale of concern here seems a dead-end. Your demand for assurances about sustainable living is of course impossible to answer affirmatively, either for "the people on this site" in general or you yourself. In communicating via this site you and I and the rest of the gang here are employing a myriad of devices and systems that are not presently built or operated in a sustainable way. What some of us may be able to say is that we try to be mindful of those occasions as are available-- in the context we find ourselves living-- which afford choices regarding making more or less of a mess. Come to think of it, your demand for pledges of sustainability is rather curious. What is it that you think "people on this site" profess? I'm wondering, do you believe that subscribing to mainstream physics and the scientific method in general is some sort of statement of moral superiority? Perhaps I misunderstand, though.
  22. Hi to JMurphy: I would be pretty miffed if my doctor had lung cancer and continued to smoke. to doug_bostrom the amount of activity this site has means that people are really bothered by this issue(s) and I would have thought that people would want to take further, bigger action towards sustainablility than just writing on web site and I am wondering if this is the case.
  23. Hapivibe @ 44 - Destruction of the rainforest which is needed for species diversity Destruction of the rainforests will also negatively impact the climate. The Amazon alone has between 86 to 93 billion tonnes of carbon locked up in it's vegetation and soils. Our oceans are being overfished And acidified too, from the combustions of fossil fuels. Which will affect fish populations at some point. So, as you can see, these issues aren't mutually exclusive.
  24. Hi dappled water I know the issues are not mutually exclusive - I am proposing that they get overshadowed.
  25. hapivibe wrote : "I know the issues are not mutually exclusive - I am proposing that they get overshadowed." And what is the basis for your proposal ? In what way do you think those issues are being overshadowed ? Is money, effort, etc. being taken away from those issues in some quantifiable way ? What's your evidence ? By the way, my previous analogy of the doctor telling you about cancer or the health-damaging effects of smoking (while being a smoker him/herself) did not involve HIM/HER having lung cancer - it involved them telling you about the detrimental effects on your life from smoking, especially if it had caused YOU to develop cancer. Would you ignore/disregard that doctor's opinion or diagnosis just because that doctor was doing something that he/she is advising you not to (anymore) ?

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