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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 101 to 125 out of 405:

  1. Sasquatch wrote (on the Could Global Warming be caused by Natural Cycles thread) : "I'm currently pursuing a M. Sci. in Environmental Systems Engineering at a major liberal arts university in the US." Do you describe some of your universities as "liberal", in America ? What does that mean ? Sasquatch also wrote : "I do not personally believe that increased levels of CO2 can initiate major changes in the climate." What do you mean by "major changes" and where have you found the sources for your belief ?
    Response: [muoncounter] Liberal arts is a catch all term used in universities to describe general studies in the humanities, math or science. It must be a fairly large university to offer a Master's in 'engineering' as well as liberal arts. It is not a political term in this context.
  2. I finally cracked open my new weather calendar. It starts with two rambling pages by Gregory McNamee detailing a few disasters but constantly pointing out benefits (e.g. dust storms fertilizing the oceans) and claiming that scientists are lowering their predictions of sea level rise. Some of what he says is ridiculous, like heavy rain being good for ducks. He ends with "Climate change is a fact. The numbers suggest other facts as well, among them that even if the world's governments too every step possible to counter that change, temperatures are likely to rise worldwide by an average of 3.6 Fahrenheit (2.6C) by the beginning of the twenty-second century. This may well profoundly alter the way our kind conducts its life on Earth. On the other hand, it is unlikely to be as catastrophic as some people fear - and that may be the best good news of all, even as we dream up news ways to keep alive, and even flourish, under a climate change regime."
  3. If the good news is that the worst of the projections probably won't happen, then the bad news is that the best won't either.
  4. Bibliovermis: MIT just updated their forecast and doubled their estimate of temperature rise. The next IPCC report will more than double the sea level rise estimate. The Arctic sea ice and the Great Ice Sheets are melting faster than the worst projections. Why do you have optimism that the worst will not happen? We need to change from BAU in order to be optomistic.
  5. Re: 103 & 104 "If the good news is that the worst of the projections probably won't happen, then the bad news is that the best won't either." "Why do you have optimism that the worst will not happen?" It won't take all of the worst happening. Some will be quite enough. BAU merely guarantees enough of the worst for overkill purposes. We live in interesting times... The Yooper
  6. I was replying to the irrelevance of Eric's quote, not giving my opinion on where reality (e.g. changes to BAU) will fall in the spectrum.
  7. David Horton, you noted in the other thread that I am in your shoes because I live on earth. I live in Northern Virginia, a climate somewhat moderated due to the Appalachians to the west, but still can be cold and dry in the winter. In the summer it can be hot and humid. I think about winter cold a lot, so I have plans for that: a southern exposure on which I already use passive solar: foundation painted black, with some acrylic (a mistake) covering and warm air intakes. I have heat mass in the crawl space. I heat with wood. There's a lot more I could do and will as I have time. I also think about summer heat and have started five shade trees. I don't worry about drought, my well is 200 feet below the river and the river will never go dry. I don't worry about floods on the river 80 feet below. My summer electric bill peaks about $50 / month with central air so I haven't done much. There simply isn't as much to do about heat except perhaps water some plants, put up shade cloth, etc.
  8. eric. that's nice. I'm not expecting Apocalypse tomorrow, or even in my lifetime. However, the papers by Matthews and Weaver, and Hare and Meinshausen for instance lead me to conclude that even if we start making changes now, it will take a long time to turn the climate ship around. There are significant risks associated with change that becomes too rapid as well - instability from climate refugees, effects from failures in food production, in particular - that I suspect will effect everyone on planet however isolated from direct effects they may be.
  9. Is it just me, or did the comment thread for both the basic and intermediate versions of this rebuttal become intertwined?
  10. Is it possible for someone to clean-up the formating of the "Cites" bibliography in the Notes section? PS -- I favor a space between each cite.
  11. First comes snow, then comes the floods of snowmelt. But this year may be worse due to the already saturated ground. NOAA Hydrologic Center: North Central U.S. Spring Flood Risk Heavy late summer and autumn precipitation (twice the normal amount since October in parts of North Dakota and Minnesota) have soils saturated and streams running high before the winter freeze-up. Another winter of above average snowfall has added water to the snow pack on top of the frozen saturated soils in the North Central US. NWS models show this snowpack containing a water content ranked in the 90 to 100 percentile when compared to a 60 year average. These factors have combined to create some of the highest soil moisture contents of the last century. NWS one-month climate forecasts show chances favor a colder than normal last month of winter across the entire North Central U.S., while precipitation patterns appear to be near normal.
  12. It's only a negative if you want your beer cold: Climatologists: "We drink beer because we care" The Yooper
  13. so as it is the right place, I post here my question : since the average population, GDP, improvement of standard of living, etc... growth has been positively correlated to temperature up to now, it must be that some other factor (whatever it is) must have been stronger, so that all drawbacks have been offset in a way or another. My question is simple : does our knowledge allow to make a definite prediction of when the correlation will be the opposite ?
  14. Gilles@113 First, as was pointed out on the previous thread, correlation does not imply causation. A more likely explanation for rising population and rising temperatures is that they both share a common cause, namely increasing economic growth through exploitation of fossil fuels. Economic growth leads to better nutrition and healthcare, which supports a larger population. Fossil fuel use leads to carbon dioxide emissions that you have said you are prepared to accept leads to warmer temperatures (how much we can leave for the climate sensitivity thread - not to be discussed further here). Of course an increase in population leads to greater fossil fuel use, greater carbon dioxide emissions and hence higher temperatures. So if anything the causal arrow goes from population growth as the cause to temperature increase as the consequence, rather than the other way around. As to your particular question, see the work of Malthus. Populations grow until they reach the limits of what the environment can support. Agriculture, improving health care, fossil fuels have all led to increased population and prosperity. That doesn't however mean that increase continues indefinitely. If climate change leads to a disruption in agriculture (for instance), then the Malthusian limit gets pushed back and we end up with at least part of the world population subject to famine. It seems to me to be quite likely that the world population is close to or at the Malthusian limit already, which is why climate change is likely to be a big problem. In short, temperature rise is no great problem for human population growth provided (i) it is not too rapid for easy adaption and (ii) the population is not close to its Malthusian limit already (that is the point where the correlation is likely to reverse). As to what we do about it, personally I would say we can't do anything quickly about population levels (doesn't fit in with my idea of ethics anyway!), so the obvious thing to to is to try and prevent the Malthusian limit on population being brought down by climate change by limiting our fossil fuel use in order to prevent great hardship (mostly in the third world). Of course that won't be pleasant for any of us, but it is better than the alternative.
  15. Gilles#113: "since the average population, ... growth has been positively correlated to temperature" Seeing something in such correlation is specious at best; at worst, it leads to yet another faulty conclusion based upon simple-minded extrapolation. One could just as easily say that population growth correlates well with a stable range of temperatures, or more importantly, a near-zero rate of change of temperature. Once out of that range or in excess of that rate of change, you have no further correlation. Another factor that is obscured by your faulty use of correlation is how interdependent the world is now. During the LIA for example, malnutrition in Europe did not necessarily impact the quality of life in Central Asia. In today's world, a problem in one continent has drastic implications on conditions around the world.
  16. Would you please update this reference under Environment in the Intermediate version of the post? Decline in global phytoplankton (Boyce 2010) It is thoroughly debunked (see all three Brief Communications linked on the paper's page at the Nature site, April, 2011). Phytoplankton in fact is not declining.
  17. Please note, re the critique of the phytoplankton paper by Boyce et al. (2010) cited @116: Boyce et al's response to the critique was, of course, not linked.
  18. #117 Albatross at 07:12 AM on 26 April, 2011 of course, not linked Here is the full exchange (open access).
  19. In economics, it's all really a matter of perception. The following is how a typical, greedy corporate who- I mean dude, could see it. Economic damage to poorer, low latitude countries Is positive for rich, high latitude countries. The poorer these countries stay, the less you have to pay for the workers in these countries. Billions of dollars of damage to public infrastructure Repairing this damage can be a great source of money for many companies. Reduced water supply in New Mexico Selling water to New Mexico can offer great amount of not only money, but political power. The less water they have, the better they can be ripped off. Increased risk of conflict (Zhang 2007) including increased risk of civil war in Africa (Burke 2009) If anything, then this is good for United States military complex and hence USA economy. As long as there are people who think like this, global warming, just like anything else, isn't going to go away.
  20. The IPSO report is out today here. Bad news: "the world's ocean is at high risk of entering a phase of extinction of marine species unprecedented in human history."
  21. Pirate, Sally Moore, et al, I think Malthus will eventually be proven correct, simply because energy available to the human species is finite. (With infinite energy, we could terraform Mars, but let's not get fanciful.) In a broad sense, the agricultural revolution was possible because we leveraged fossil energy to produce more food. Now we are bumping into other limits: a reduction in the availability of fossil fuels to produce fertilizers and pesticides and drive tractors, arable land, and changes or exhaustion of supplies of water for irrigation. At the same time there is a shifting of climate zones and general disturbances in weather patterns which can only hurt the yields of industrial agriculture. How much we degrade our food supply depends a lot on how much climate change we induce. It is not going to be just agriculture, we are already severely stressing oceanic fish, and acidification represents a threat of food web destabilization. Whatever numbers you project, an increase in population at the same time as a reduction in food supply is some uncomfortable math. Given the current state of things, and the lack of any progress in the last decade, my guess is that a bottleneck in human population is inevitable. In that light, I understand Pirate's attitude. However, how much of a bottleneck remains to be seen, world war level, black plaque, something less, or something more. If we can avoid an anoxic ocean event, the species will likely survive. But, just because you believe you can not avoid a car wreck is no reason not to shift your foot from the gas to the brake. It might make the difference between minor injury at one end of the range of possibilities and death at the other. Since we have no record of changes to the climate as rapid as the one we are causing, we only have educated guesses as to what will happen. Skeptics decry the uncertainty of climate models, but I don't know of any credible ones that paint a rosy picture. As has been said before, uncertainty is not our friend. How many of us survive is still important. Thinking of yourself, your friends, and family, is it better that 1 of 20 die, or 3 of 10? Continued BAU for too long increases the likelihood of that first number becoming zero. So, Sally, I'm not a scientist, but I also worry, a lot. My sister has decided not to have kids. I'm more optimistic, or maybe I just don't want to give up, or maybe it was a biological urge I could not resist, or maybe I'm egotistical enough to think the world is better off with more people like me. I raise my own kids to be as strong and independent minded as I know how, with as broad an experience and educational background as I can give them. Parents have always done this, but I think the coming generations will suffer more than most past generations have from living sheltered lives.
  22. Chris G @ 121 Nicely written. I am not callous. Just realistic. Human history is rife with events that reduced our population size on regional and global levels whether it be plagues or natural disasters. And, we should absolutely be good stewards of the earth. I think it is smart for you to teach your kids to be strong and independent. I do the same with mine and I am trying to teach them survival skills. I am sorry your sister has decided NOT to have kids. The Earth is a dynamic planet. Changes are always occurring. We have the capacity to adapt and will. Human survival many generations from now, may depend on us leaving the planet.
  23. pirate#122: "Human survival many generations from now, may depend on us leaving the planet." Whoa! That science isn't settled. Which planet would we go to? Planets would have to be 'rated' by an independent authority, preferably someone with no actual expertise in planetary science. And the cost of leaving the planet would destroy our economy. 'Scientists' involved in space flight would get rich on the free-flowing government money. Anyone who questioned leaving the planet would lose their job. It all sounds like a c--spiracy to me.
  24. In a spirit of refinement: Under "Polar Melting" the last sentence (as I write) is "Melting of the Antarctic ice shelves is predicted to add further to sea-level rise with no benefits accruing." If ice shelves are floating ice (rather than land based ice), why would their melting per se particularly add to sea-level rise? What scientist has predicted that? Suggest removing that sentence. Sea level rise is covered under another bullet point anyway. (Yes, there could some side effect of speeding the adjacent land based ice's speed of travel to the sea - but that's more indirect and less solidly demonstrated and generally not what the sentence says or needs to say).
    Response:

    [DB] Thanks for taking the time to add to the discussion. 

    "If ice shelves are floating ice (rather than land based ice), why would their melting per se particularly add to sea-level rise?"

    Excellent, thoughtful question.  Obviously, floating ice itself cannot add to SLR as it melts.  A general answer is that the floating ice sheets of Antarctica act as buttresses, inhibiting/slowing the downstream flow of the ice sheet proper in response to gravity.

    A loss of the floating ice sheets will lead to the oceanic edges of the ice sheet to exposure to the much warmer waters of the Southern Circumpolar Current.  This will then lead to greater rates of calving at the leading edges, which then leads to an increase in icestream flow downhill.  This vector change in icestream speed eventually propagates upstream along the entire channel of ice.  The result is dramatically increased rates of calving of ice leading to the demise of first the WAIS (West Antarctic Ice Sheet).  Given enough warming and enough time, the EAIS (East Antarctic Ice Sheet) will also be vulnerable.

    Remember, the base of the WAIS and most of the EAIS are well below sea level.  The body blows the ocean can land without the blocking arms of the ice shelves can wreak terrible impact.

  25. Continuing from here. ClimateWatcher: "our ancestors were not troubled by natural variations in climate" Tell that to the Anasazi: Climate change is thought to have led to the emigration of Chacoans and the eventual abandonment of the canyon, beginning with a 50-year drought in 1130. Tell that to the Akkadians: Geochemical correlation of volcanic ash shards between the archeological site and marine sediment record establishes a direct temporal link between Mesopotamian aridification and social collapse, implicating a sudden shift to more arid conditions as a key factor contributing to the collapse of the Akkadian empire. Tell that to the Mayans: A seasonally resolved record of titanium shows that the collapse of Maya civilization in the Terminal Classic Period occurred during an extended regional dry period, punctuated by more intense multiyear droughts centered at approximately 810, 860, and 910 A.D. And tell it to whoever these folks were. A severe drought in parts of low-latitude northeastern Africa and southwestern Asia ~4200 yr ago caused major disruption to ancient civilizations. Seems like drought is a common theme in these 'troubles'. This drought forecast should be troubling: Or as one Texan put it more succinctly,

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