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Positives and negatives of global warming

What the science says...

Select a level... Basic Intermediate Advanced

The harmful impacts of climate change, which have the ability to alter ecosystems and expose society’s vulnerabilities, significantly outweigh any beneficial impacts that may arise.

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)

The Pros and the Cons

Our current climate crisis poses an existential threat unlike any that our species has experienced before. Emerging evidence suggests that the rapid increase in global average temperature will wreak havoc on not only our climate system, but also our day-to-day lives. In 2019, global average temperature was 0.99 °C (1.78 °F) above the 1951-1980 average temperature. While we are already seeing the effects of a changing climate, scientists warn of significantly worsening impacts if warming is not kept below 1.5 °C. These severe impacts can include substantial land and sea ice loss, ocean acidification, changes in ocean circulation, and shifts in weather patterns which ultimately lead to food and water shortages along with economic and social unrest.

There are also ways in which society may benefit from a warming climate. Reduced sea ice will open more passageways for ships and will allow the poles to be more accessible. A warmer climate may grant certain areas, especially northern latitudes, longer and earlier growing seasons. Warmer winters mean less cold-induced deaths. Increased carbon dioxide levels may help vegetation to flourish for a greener world. Unfortunately, though, many of these benefits are short-term and are greatly overshadowed by the negative impacts that climate change brings.

Land and Sea Ice Loss

Ice is an important part of the global climate system because it reflects a large amount of solar radiation while also moderating global sea level. As ice melts, the less reflective ocean surface is exposed and instead of radiation being reflected, it is absorbed and causes more ice melt. This is called a positive feedback system, which is what makes polar regions so sensitive to climate change. High northern latitudes are experiencing rapid warming due to polar amplification causing land and sea ice to melt at an increasing rate.

Measurements show that the central Arctic has seen a decrease of over 50% in sea ice thickness along with an average decrease in September sea ice extent of 130,000  per year from 1997 to 2014. If warming exceeds 1.5 °C, models predict Arctic summers to eventually become ice free. In Antarctica, ice melt varies greatly with net ice loss in some regions and net ice gain in others. One of the biggest areas of concern here is the West Antarctic Ice Shelf (WAIS). The WAIS has been seeing a rapid decrease in mass with a loss of up to 200 Gigatons (that is 200 billion metric tons) per year.

Other ice formations such as snow cover and frozen soil called permafrost have also been melting at staggering rates. From 1967 to 2012, June snow cover in the Northern Hemisphere has decreased at a rate of 11.47% per decade. In response to this, permafrost layers have warmed and thinned. For up-to-date ice loss measurements, the National Aeronautics and Space Administration (NASA) has a website that provides graphics and numerical data. Substantial loss in both land and sea ice can result in changes in weather, ocean thermohaline circulation, and sea level rise due to reduced solar radiation reflection and more water being added to the oceans.

Sea Level Rise

Paleoclimate data suggests sea level has risen and fallen many times throughout Earth’s past. Land ice formation and melt lead to a rise or drop in sea level. Sea level is also dependent on thermal expansion, the process of water taking up more space as its temperature increases. About three million years ago, when carbon levels were similar to what they are presently and there was less ice coverage, global average sea level was roughly 80 feet higher than what we see today.

With atmospheric carbon levels continuing to rise, global average temperature increasing, and consistent ice melt, climate scientists predict we will experience considerable sea level rise in the future. In fact, we already are. Using tide gauge and satellite altimeter data, the Intergovernmental Panel on Climate Change (IPCC) concluded that the global mean sea level rose 0.19 meters from 1901 to 2010 with a rate of up to 3.2 millimeters per year. Climate models predict that the rate of sea level rise will increase to 16 millimeters per year by 2100 but will not be a uniform global event. With an estimated 70% of coastlines affected and about 40% of the world’s population living within coastal regions, a sea level rise of just a couple meters will displace billions of people and dramatically alter their day-to-day lives.

Ocean Acidification and Circulation

The atmosphere and ocean are constantly exchanging properties such as temperature, water, and even gases. Thus, as we put more carbon dioxide into the atmosphere, we are also putting more carbon dioxide into the ocean. This exchange of carbon is essential to both parties but when the ocean receives too much carbon, a process called ocean acidification takes place through the chemical process shown in Figure 1. Research predicts that by 2100, the ocean will become 15-17% more acidic compared to current pH levels. A more acidic ocean would be a lethal environment to most marine species which, in turn, will greatly impact humans, especially those who depend on our oceans for food.

As our present-day climate rapidly changes, a disruption in ocean circulation is also becoming an area of great concern. Thousands of years ago during times of abrupt climate change such as the Younger Dryas, it is believed that oceanic thermohaline circulation was slowed or halted thus altering both oceanic and atmospheric behaviors. Today, an important mechanism involved in this circulation is what scientists refer to as the Atlantic Meridional Overturning Circulation (AMOC). Atmospheric temperatures greatly impact thermohaline circulation (hence “thermo”) therefore a warming climate may alter ocean circulations such as AMOC. According to the IPCC, rising greenhouse gas emissions are likely to cause an 11% deceleration in AMOC by the end of the century. The main purpose of ocean circulation is to transport heat, water, and nutrients between the equator and poles. A cessation in this can cause numerous unwanted effects such as changes in marine ecosystems, large-scale convection, air-sea interactions, and wind patterns as the climate system tries to compensate for the loss of vital transport.


Figure 1 illustrates the process of ocean acidification. 

Weather Events

Climate change not only affects temperatures, it also affects cloud formation, tropical cyclone development, and everything in between. Civilization has long depended on precipitation events for water and agriculture. Patterns in these events were fairly predictable during a steady climate but a changing climate ushers in much variability which may lead to long-term droughts or floods. If warming reaches 1.5 °C above pre-industrial levels, the IPCC predicts that there will be a 100% increase in flood risk in areas such as the United States, Asia, and Europe. Relatively dry regions such as the American Midwest are expected to face more frequent and intense droughts.

Monsoon systems are likely to impact larger regions and intensify while precipitation related to El Nino Southern Oscillation is expected to increase. Since 1970, the North Atlantic has seen surges in tropical cyclone intensity and climate scientists predict that there will likely be more frequent and intense storms in the future. It is important to note that although climate models suggest these shifts in weather events, scientists believe these predictions are subject to change, but are still likely to happen, due to the numerous other factors that affect the development of meteorological events. As discussed later, these changes in weather events will greatly impact water and food resources.

Tipping Points

One particularly extreme and, frankly, frightening topic that vastly outweighs any possible beneficial impacts is what climate scientists call tipping points. A tipping point is reached when a vital component of Earth’s climate system rapidly changes and enters a new state. In the climate system, a variable will change so much due to the warming climate that it will reach a point, its tipping point, where it is in a completely new state. Climate scientists believe that reaching tipping points in ice melt, ocean circulation, rainforest deforestation, and coral reef bleaching may push the climate system as a whole to a new state. In addition, tipping points do not exist in isolation. They are all interconnected, meaning that reaching one tipping point can trigger another one which, in turn, triggers yet another one.

Food, Water, and Health

The percentage of the world’s population experiencing water scarcity went from 14% to 58% in just the last century. In 2016, roughly 815 million people were malnourished. With much of the world already struggling to access clean water and food, it comes as no surprise that climate scientists are predicting significant losses in crop yield and clean water, due to climate change-induced droughts or floods, along with degradation of human health as a result of the warming climate. Some climate models are suggesting an additional 8% of the world’s population will see a large reduction in water availability in 2021-2040 along with significant changes in food production. Concerns of other health risks such as diseases, air quality-related mortality, and temperature-related mortality are also being raised. The elderly, children, low-income families, and those with pre-existing conditions are among the populations with greatest climate change-induced health risk. Higher temperatures and degrading air quality will allow for increasing cases of diseases such as malaria, respiratory illnesses, and heat exhaustion.

Economics and Social Unrest

Food and water scarcity can lead to higher prices and disputes over access to these necessities; therefore, nations experiencing low food production and poor water quality with an unhealthy population will inevitably experience severe economic distress and social unrest. The changing climate is expected to send up to 16 million people below the poverty line and possibly displace millions from their homelands. Data suggests that hunger, thirst, and economic hardship due to climate change will increase social unrest and conflicts by 14%.

When in Doubt… Cherry Pick

A common climate myth states that climate change may be beneficial. This myth commits the fallacy known as cherry picking, meaning that climate science deniers essentially ‘pick’ out information that could be used to support their argument while simultaneously ignoring scientific facts that prove the opposite. In this case, the myth focuses solely on the few positive impacts of a warming climate which diverts attention away from the mounting evidence that a rapidly warming climate will wreak havoc on all aspects of society.

Figure 2 shows risk severity dependent on global average temperature (°C) above pre-industrial levels (1850-1900). 


Scientific research continues to prove that the negative impacts of climate change far outweigh any positive impacts. Our modern-day climate crisis has ushered in a host of problems for society to solve. If reached, a warming of 1.5 °C above pre-industrial levels will cause land and sea ice loss, sea level rise, changes in ocean circulation, ocean acidification, extreme weather events, exacerbation of tipping points, poor human health, and social unrest. Consequently, much of society will be left without food, fresh water, and shelter. But, if we listen to the science, we will have within our power the ability to take action to save not only ourselves, but also our planet.

Last updated on 14 November 2020 by sophia_whitaker. 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 1 to 25 out of 425:

  1. This NY Times article apparently refers to the following document: “Estimating Future Costs for Alaska Public Infrastructure At Risk from Climate Change”
    Response: Many thanks, I've updated the link (under Economical) - always good to go direct to the source!
  2. Malaria spread? It already reaches the Arctic circle how much more could it spread? I know tongue in cheek but some of these things are mutually exclusive.
  3. Malaria is one among others. Italy recently had a brush with Chikungunya (more fun to pronounce, if not to experience). Dengue fever is also to be considered Furthermore, "skeptics" take as fact the idea of "CO2 fertilization" popularized heavily by the propaganda site called CO2Science. However, that fact may not be nearly as much good news as they imagine. Those positives and negatives are still pretty much open to speculation, I remain quite skeptical of the "CO2 fertilization" idea in light of the open air experiments conducted so far.
  4. "Those positives and negatives are still pretty much open to speculation, I remain quite skeptical of the "CO2 fertilization" idea in light of the open air experiments conducted so far." 1. Every last open air experiment so far has CONFIRMED the fertilization effect. 2. Open air experiments may appear to be "streetwise" but they are very much likely to UNDERESTIMATE the CO2-fertilisation effect. Open air experiments sound to me like an appalling waste of money. You either control a factor in an experiment or you do not. Piping CO2 into the area isn't going to have the same effect as having the CO2 homogenised in the air. Since the plant is accessing the CO2 at the molecular level and not at the level of little eddies and wisps of unhomogenised CO2. What looks at first like the streetwise simulation on second thoughts appears to be hopelessly unrealistic. And it appears to underestimate the massive and universal benefit of extra CO2. But nonetheless these experiments CONFIRM this universal benefit. They underestimate the benefit but still they confirm the benefit.
  5. What makes you think that the limits on Rubisco Activase will not manifest themselves? How could it be good to shift the ratio of ATP/ADP toward ADP? Since CO2 level is already quite a bit higher, those bumper crops should already start to show up. Examples? Universal benefit? How is it universal?
  6. And if you dig, you find stuff about methane hydrates and the P/T extinction, so it is a stretch to say there is no justification whatsoever of dire predictions. I'd say that it would be as much of an exaggeration than to predict bumper crops on the basis of the existing CO2 fertilization alone.
  7. In other words Malaria should be removed from the list. Maybe there are other diseases but Malaria which already exists in the Arctic is not one of the bugs that is likely to increase its range due to climate change so its inclusion here is simply wrong. Other diseases would also have to be evaluated case by case and there are many if not more illnesses associated with low temperatures. I haven't had time to research many of these claims but the few I have researched on the negative side are very doubtful, like polar bears being threatened, which is directly contradicted by the available data. This is an old salesman trick of inflating the number of arguments on your side and minimizing the number on your opponents side. It doesn't impress me and it does the AGW argument more harm than good.
  8. Mostly pure speculation; extrapolation without including negative feedbacks is useless and as WA. says, harmful to the argument. ? expanding desert areas? Look at the existing deserts and tell me how they formed and grew BEFORE any AGW effects. Oh, and right now Egypt has drilled over 100 wells into the Sahara bedrock and (so far) found sufficient fresh water for the next 500 years. Thank you satellite radar imaging which showed the underlying ancient river courses and lakes. The same technology shows similar ancient water deposits in Darfur ( the war there is directly attributable to scarcity of water) and the government there has been offered the expertise to explore it...which could end that conflict and turn the country into an oasis. My Point? All the doom and gloom projections NEVER NEVER can account for paradigm shifts caused by technology. ( NY was predicted to end up knee deep in horse **** in the 1800's because of exponential increases in the use of never happened, instead, the automobile did). My point?
  9. What about global warming reduces heating fuel consumption? Philippe: We should hold very lightly info that doesn't have empirical data tacked onto Co2 fertilisation ( or lack of it) Jasper Ridge have been conducting controlled experiments on plants for the past 3 yrs and their data shows 1/3rd increase in biomass if CO2 alone is increased, and up to 85% increase if water/minerals/ temp are optimised WITHOUT extra CO2.
  10. From the Ministry of Ag, Ontario: "The benefits of carbon dioxide supplementation on plant growth and production within the greenhouse environment have been well understood for many years... For the majority of greenhouse crops, net photosynthesis increases as CO2 levels increase from 340–1,000 ppm (parts per million). Most crops show that for any given level of photosynthetically active radiation (PAR), increasing the CO2 level to 1,000 ppm will increase the photosynthesis by about 50% over ambient CO2 levels. For some crops the economics may not warrant supplementing to 1,000 ppm CO2 at low light levels. For others such as tulips, and Easter lilies, no response has been observed." Commercial growers all over the world have invested millions of $ into CO2 enhancement of greenhouses: Given that they are businessmen, if there was no appreciable crop increase they wouldn't be doing it- No? Now I would call a 50% increase in crop mass substantial, maybe not BUMPER, but clearly enough to warrant the cash investment. So there is plenty of empirical, current, evidence that raising levels of CO2 causes plants to grow bigger and faster. It isn't an issue, it's a fact. Just as clear is that concentrations up to 1000ppm the Rubisco Activase limit does not manifest.
  11. Can Carbon Dioxide Be A Good Thing? Physicist Explains Benefits Of Carbon Dioxide June 1, 2007 — A physicist from Colorado State University and his colleagues from the North American Carbon Program (NACP) have discerned and confirmed the unforeseen advantages of rising carbon dioxide levels. Through the processes of photosynthesis and respiration, scientists have been able to elucidate why plants are growing more rapidly than they are dying. The NACP is employing methods, such as the use of cell phone and aircraft towers to monitor and retrieve carbon data for their continuing study.
  12. Well John after much reading I think this is a thread where you are likely wrong. I have read a lot of claims that CO2 increasing yields is a myth, however in controlled experiments it really tends to have a large positive effect. Some have even claimed that it doesn't work in the "Real World".. A good argument sometimes but one that doesn't work very well here. If CO2 increases yields under controlled conditions but this is not seen in the real world that would in fact strongly suggest that our readings of CO2 increasing were incorrect not that CO2 doesn't help. That would be an interesting thing to investigate.
  13. Lets look at this from a logical perspective. Warmer means more like the world that we evolved in during the PETM (when prosimians first appear) in Asia. Colder means more like the world that came close to driving us to extinction (glacial maximum) in Africa. We are from a tropical paradise, no polar ice caps and green pole to pole. Which do we wan't for our offspring? Warm and abundant or cold and starvation?
  14. #14....Most of the examples of increased CO2 giving increased plant growth have come from environments where the CO2 level is artificially held at around 1000ppm. In the real world the levels have risen from around 260ppm (1000AD) through 290ppm (1900AD) to 380ppm (2005), in other words the increase over the period we have started taking interest in what's going on is at best 100ppm. Roughly, doubling the level gives a 50% increase in growth, so adding a third (real world) isn't going to show up much at the small scale level. Globally, however, the increase may be significant, although probably unquantifiable
  15. A good book on this topic: This book has hundreds of references to objective peer-reviewed studies on the effects of global warming, at each degree C in global temperature rise. Essentially, costs immediately exceed benefits. With each degree of warming, the cost-benefit gap expands greatly.
  16. Millions of years ago, climate conditions were such that plant life grew rapidly on a global scale. CO2 and WV levels were high enough to sustain this growth and during this period much of the FF's we now burn were laid down. Plant life sequestered CO2 and locked it up as FF, thereby reducing the CO2 levels, although at times, 'natural' events such as vulcanic erutions/forest fires would have temporarily offset this sequestration. The end result is that CO2 levels hit (possibly) an all time low of around 200ppm and stayed there. As this level is close to the minimum C3 plants can tolerate, further growth and investment of new habitat were resticted. At this time, only C3 plants existed (fossil records of C4 plants indicate their emergence around 8mya) and C3 plants, in order to prosper, require CO2 levels higher than 200ppm. If the levels fall below this figure, then growth effectively halts as does sequestration. One can argue that the emergence of C4 plants was 'caused' by persistent low levels of CO2 - an adaptation of metabolic process to environmental pressures - and since they are more efficient in their use of CO2,(they had to be) they began to colonise and modify habitats where C3 plants could no longer compete effectively. C4 plants are grasses, and include the cereals. The rise of civilisation was made possible only because of these plants and man's ability to husband them, so we actually owe our existence to low levels of atmospheric CO2. Current concern is directed at enhanced CO2 levels through burning FF's, and the (modelled) effects this may have on climate, and the consequent impact on man's habitat. The current level of around 380ppm, whilst nearly double that during the period C3 plants were dominant, is still towards the lower level of tolerance for them. It can therefore be argued that further increases of CO2 will be beneficial to this class of plants and not detrimental to C4's until levels exceed 1000ppm; in other words, our CO2 emissions are helping C3 plants, and quite possibly helping (in some small way) to offset the losses incurred by de-forestation. Yes, they may be disadvantages to mankind and his preferred lifestyle/habitat from CO2 enhancement, but there are benefits to the biosphere at large.
  17. High Carbon Dioxide Boosts Plant Respiration, Potentially Affecting Climate And Crops ScienceDaily (Feb. 10, 2009) "The leaves of soybeans grown at the elevated carbon dioxide (CO2) levels predicted for the year 2050 respire more than those grown under current atmospheric conditions, researchers report, a finding that will help fine-tune climate models and could point to increased crop yields as CO2 levels rise."
  18. "This book has hundreds of references to objective peer-reviewed studies on the effects of global warming, at each degree C in global temperature rise. Essentially, costs immediately exceed benefits. With each degree of warming, the cost-benefit gap expands greatly." How much colder should the earth be to idealize the benificial ascpect for man. Of course I am most intested as to what "peer reviewed" studies have concluded. Another thing I am most intersested in is what "peer revied studies" have concluded thet the DOW jones should be at by the year 2025. Dont you alarmists have any sense of humility as to what you think you know. For the record "peer review" is simply a call for rudimentary error checking - it is not thesis confirming and it is by no means systematic, thorough, or even unbiased. It has its place but it is neither an essential nor required component of sound science. Theory confirmation is derived by outcome - not opinions of self proclaimed "experts"
  19. Some of your pros and cons listed above and not correct. The longer geological record contradicts statements made by the IPCC and other climatologists, because the IPCC and other climatologists don't usually bother to consult the longer geological record, and the usual argument from climatologists is that 'geologists are not climate scientists', which is false; climate is a subset of geology (earth science), not the other way around, (with both ultimately a subset of astronomy). The longer geological record has much to say about the lists you have given above, for eg: -Increased desertification corresponds to globally cool periods, NOT warm periods, in the geological past, (which is the opposite of what the IPPC projects). This genrally means that African and the US, and some Asian crop yields will increase with warming, not decrease. Globally, there is more rainfall. Africa, for example, began to become drier with the onset of glacial periods several million years ago, with larger areas of savannah and reduced rainforest cover, (which may well have led to the evolution of the savannah-ape line-that's us). -Warm periods do not correspond with increased extinction in the geological record, rather, biodiversity increases (which is the opposite of what the IPCC projects) -Coral reefs thrive during sea level rise, whilst sea level falls produce extinction. -Coral reefs thrive during warmer periods, and oceans do not become acidic from greatly increased C02; there were many periods of thriving corals and other marine life in the geological record when C02 was much higher than today. -Polar bear populations have survived the many warm interglacials in the last several hundred thousand years, warmer periods do NOT promote their extinction. The bigger threats to polar bears are ecotourists, bureaucrats, and hunters. -The Tibetan plateau began to rise around 30-40 million years ago; changes in short -term climate are paradoxical and not thought to greatly affect water supply/runoff in this region as much as longer period changes in elevation; as during globally warmer periods snow (and rain) precipitation increases along with seasonal meltwaters-particularly on the Chinese (cooler) side, whilst in cooler periods ice and snow cover increases but overall precipitation and seasonal meltwater generally decreases. Other points: -Crop yields at all latitudes increase with increased C02, (already an estimated 15% since about 1850), the same goes for tropical rainforests,(the Carboniferous period had high vegetation levels and high C02-much higher than at present) -Both Europe and USA have thrived in warmer periods, both ecologically (in the past) and economically during human occupation eg reduced energy consumption for heating, increased rainfall, less droughts, less deserts (USA). -Lakes do no "vanish" on a global scale during globally warmer periods; if anything it is generally the opposite (point 1 above-lower desertification occurs during warmer periods). I could dig up alot of other longer geological record indices, but again, what surprises me is the complete ignorance amongst many who promote various global warming scenarios/projections on what the actual record of the earth itself has to say on these matters. A similar thing occurs with creation scientists, and in various discussions and debates within biology about evolution; the longer geological record is usually ignored (other than the usual-'the fossil record is incomplete'), when it was the geological record that formed the general foundation about thinking about evolution in the first place, and has alot to say about it. Another related topic is the long history of debates around catastrophism and uniformitariaism-which also have much to say about current issues/debate concerning global warming-but that is for another day and another thread. In general, there needs to be more input/integration from the actual geological record on various climate change scenarios/issues, which directly contradict some of the (surmised/projected) points in your list above.
  20. Plants can't grow any better than their limiting factor, which might be not CO2, but nitrogen, water, light,.... Some plants grow worse at higher temperature, offsetting gains from CO2 spurring growth. Even if they do grow "better," the betterment often is not to the advantage of farmers; for example, the extra mass can go into non-consumable woody stalk, which makes the crop more expensive to process than any extra grain/fruit value. And weeds such as poison ivy and kudzu respond much "better" to increased CO2 than do many crops, but "better" is not better for people, and not better for plants that those weeds compete with. For details see the U.S. Department of Agriculture's report on climate change.
  21. I feel that the positives vs. negatives are somewhat biased toward the negative side. For instance, on negative, it says decreased water levels three times, and specifies each individual area where the water supplies will decrease each time: * Decreasing human water supplies... (Solomon 2009) * Decreased water supply in the Colorado River Basin (McCabe 2007) * Decreasing water supply to the Murray-Darling Basin (Cai 2008) However, on positive, it only says: Improved agriculture in some high latitude regions (Mendelsohn 2006) It does not specify what countries or regions, which could inflate it to several points. Seeing as that has been done with the decreasing water supply, I think the same should be done for the positives.
    Response: This is solely because I'm referencing individual papers. I suggest you take a leaf out of Shawnhet's book and find some positive papers focusing on benefits in specific regions.
  22. Re Glacier Melt, Barnett 2005, Kehrwald 2008 and 'Severe consequences for one-sixth of world's population dependent on glacial melt for water supply': I wasn't going to bother with this tabulation any more (for reasons already given) but I can't let this slide. Barnett's 'one sixth of the world's population' refers to both snowmelt and icemelt - mostly the former, of course. Kehrwald's 'one sixth' is either a misattributed misrepresentation of Barnett or pure invention. Either way, it's gibberish. If you're genuinely interested in presenting a fair picture of the science, the least you can do is remove the Kehrwald reference and add something that highlights the importance of snowmelt to this alleged one sixth. Personally, I'd remove the whole thing. Barnett was based on a very dodgy analysis.
    Response: I notice Kehrwald 2008 cites the IPCC AR4 as their source so until I track down the IPCC's peer-reviewed source (most likely Barnett 2005), I've removed Kehrwald. I find it interesting that you'd 'remove the whole thing' - do you think the whole issue of threatened water resources for such a large proportion of the population is not worthy of concern?
  23. JC: 'I notice Kehrwald 2008 cites the IPCC AR4 as their source so until I track down the IPCC's peer-reviewed source (most likely Barnett 2005), I've removed Kehrwald.' Would that help? Kehrwald et al. offers several contradictory estimates of the number of people in South and East Asia who rely on water from melting glaciers. Would a peer-reviewed source for any of them really confer legitimacy on self-evident nonsense? Kehrwald's largest estimate: 'TP ice fields are a critical resource for one sixth of the world’s population'. 'TP' is 'Tibetan Plateau'. In Kehrwald, 'Tibetan Plateau' has at least three different meanings. Let's assume that this one was 'Himalayas plus Karakorams plus Hindu Kush plus Pamirs plus the Tibetan Plateau proper and the mountains on its western and northern rims'. Are the glaciers in this large region a 'critical resource for one sixth of the world’s population'? Er, no. Does any peer-reviewed literature say that they are? Probably. Does Kehrwald's cited source say that they are? No. The 'one-sixth' claim was attributed to AR4 WG2 Chapter 10, which says nothing of the kind. If not pure invention, it was probably a misattributed mangling of Barnett, which claimed (on very dodgy grounds) that 'more than one-sixth of the Earth’s population [relies] on glaciers and seasonal snow packs for their water supply'. Snow *and* glaciers. Worldwide, not just 'TP'. And note that Barnett's 'one-sixth' didn't include people living on the Gangetic plain. (He got something right.) The only other attributed claim in Kehrwald (750 million seriously affected) comes, it is said, from the Stern Review via WG2 Ch10. Stern did say something like that but its cited sources didn't support it. Things get complicated here, so I won't go further unless you insist. JC: 'I find it interesting that you'd 'remove the whole thing' - do you think the whole issue of threatened water resources for such a large proportion of the population is not worthy of concern?' I find it interesting that you are happy to accept that the water resources of such a large proportion are threatened. Peer-reviewed crap is still crap.
  24. Vinny Burgoo at 11:37 AM on 11 March, 2010 When assessing the importance of any single component of a population's water supply, it is important to remember that water needs to be available always, and the available quantity required at any given time is bounded by definite lower limits. I've seen a lot of criticism of water supply impacts based on the notion that "only" 20%, 10% or 5% of a given total regional water supply is sourced by glacial and snowpack meltwater. If during certain times of the year the component that is only 20% of an annual supply represents 50% of the instantaneous available flow, the perspective of persons depending on that supply will be rather different than for those of us sitting in our armchairs at safe remove, wondering what the problem is. Not to be repetitious, but tell an engineer that you're going to remove reservoirs supplying 20% of a water utility's capacity and he should not worry because the annual total amount of water passing by his system will remain the same and that engineer will think you crazy. As to the rather arbitrary separation of snow and ice meltwater sources, if as we can expect glacier disappearance is accompanied by more rapid melting of snow the current budgetary components of melt water sources are of less use in predicting future impacts of glacier loss. This hair-splitting about impacts of changes in regional water supplies resulting from warming is at the end of the day not very flattering to so-called skeptics. Rummaging around for minor flaws in citations is not a robust counter-argument.
  25. Robust counter-argument against what, doug_bostrom? It's certainly a good argument against political overreaction. Does it really not concern you that bogus claims are being made about the water supplies of one-sixth of the world's population? (Yes, I did read your lecture about seasonal flows etc. Meltwater from Kehrwald's 'TP' glaciers mostly coincides with the monsoon, when the glacial component is more like 2%, not 20%. So where is this one-sixth of the world's population? Not in the oases of Western China, which do rely to some extent in summer on glacial melt. That's most likely bad news for tens or scores of millions who live there but 100 million is not 1000 million. Exaggeration is neither scientific nor big nor clever. Also, your conflation of snow- and glacier-melt was... unhelpful.) Like many of your stripe, you are hung up on the denial of the theoretical basis for AGW. Things have moved on. Impacts are what matter and the science of predicting impacts is demonstrably weak and overstated. The whole field is less than scientifically kosher and large areas of it are politicised. It really shouldn't be up to ordinary 'hair-splitting' citizens to sort this out. It takes hours and days for a non-specialist to track back a single claim to its source and evaluate it. The IPCC is supposed to have done all that for us. It hasn't. I'm pissed off. Don't be surprised that a lot of other people are pissed off. And if you're not pissed off too, that isn't very flattering to you, especially when you're posting on a website called Skeptical Science. (Pre-emption: Yes, Kehrwald et al was published post-AR4. Will it be in AR5, though? Let's bloody hope not. Barnett too.)

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