Talk:Climate change/FAQ

This page lists questions and assertions that have come up repeatedly on the talk page of the articles related to global warming.

This is not an article; it is part of an article talk page. The answers on this page may be a matter of dispute on the main talk page. Each answer represents the most commonly held scientific view.

Please note that this page does not constitute any part of the article space for wikipedia, and only exists as a useful place to put frequently asked questions and their frequently given answers. Do not use this as a debating place. Feel free to add other common question/answer pairs, or alternative answers, that are properly sourced in the scientific literature.

Is there really a scientific consensus on global warming?

• Yes. The IPCC position has been derived using a consensus process. This has been recognized by a number of prestigious scientific organizations and reinforced by independent analysis of the scientific literature, see Scientific_opinion_on_climate_change#Oreskes.2C_2004.

Water vapour is the most important greenhouse gas!

• See Greenhouse_gas#The_role_of_water_vapor and Greenhouse_effect#The_greenhouse_gases for details.

  Water vapour is indeed a major greenhouse gas, and contributes significantly to the greenhouse effect. But water vapour has a very short atmospheric lifetime (about 10 days) and is very nearly in a dynamic equilibrium in the atmosphere, which globally maintains a nearly constant relative humidity. Increased temperatures will increase the absolute amount of water vapour in the atmosphere, and hence the greenhouse effect. This is an example of a positive feedback effect. Thus, while water vapour does not act as a climate driver, it does tend to amplify existing trends.

There is a substantial segment of the scientific community that strenuously disagrees with the premise that global warming is dooming our planet

• This page is about the science of global warming. It doesn't talk about planetary doom or catastrophe.

Scientists only support global warming to get more money

• Scientists participate in international organizations like the IPCC as part of their normal academic duties. They do not receive any extra compensation beyond possibly direct expenses.
• Scientific grants do not usually award any money to a scientist personally, but only towards the cost of his or her scientific work.
• In the U.S., global warming is seen as a politically sensitive topic under the present administration, and this discourages scientists from working on the topic.[1]
• It could also be argued that more money lies in examining the policy debate on global warming. [2] [3]

It was obviously much warmer when the Norse settled Greenland

Greenland was not significantly warmer during the period of Norse settlement. While much of Greenland was and remains under a large ice shelf, the areas of Greenland that were settled by the Norse were coastal areas with fjords that, to this day, remain quite green. Please see the following images for reference:

• A map of the Eastern Settlement [4]
• A satellite image of that area today [5].
• A map of the Western Settlement [6];
• A satellite image of that area today [7].
• A zoom in on the general area where the Brattahlid and Gardar farms were located [8].
• A zoom in on the general area of the Sandnes farm [9].
• Ruins:
  • Photos of the Gardar ruins: [10] [11]
  • The Brattahlid ruins [12] [13]:
  • Hvalsey church: [14]

The IPCC reports are prepared by biased UN scientists

• The IPCC reports are not produced by "UN scientists". The IPCC does not employ the scientists who generate the reports, and has no significant control over them. The scientists are internationally recognized experts, most with a long history of successful research in the field. They are employed by a number of different organizations, including scientific research institutes, agencies like NASA and NOAA, and universities. They receive no extra pay for their participation in the IPCC process, which is considered a normal part of their academic duties. The latest (fourth) IPCC report was prepared by over 850 authors and reviewed by more than 2500 expert reviewers from all over the world.

I don't believe that global warming is happening or that it is caused by human activity!

• If you have documented evidence from the peer-reviewed literature, or if you have other information that meets standards of verifiability and reliability and no original research consider adding it to the article. Also remember that neutral point of view requires that minority perspectives should not have equal prominence with majority perspectives. There are many forums which welcome discussions of global warming but this is not a forum. Please limit your talk page comments to improving the article, not discussing the topic.

Mars (or Jupiter, or Pluto) is warming, too (so it's the sun!)

Further information: Climate of Mars

Further information: Extraterrestrial atmosphere

• A 2007 National Geographic article described the views of Khabibullo Abdusamatov, who claims that the sun is responsible for global warming on both Earth and Mars. Abdussamatov's views have no support in the scientific community. Indeed, the second, apparently rarely read page of the National Geographic article makes this clear: "His views are completely at odds with the mainstream scientific opinion" said Colin Wilson, a planetary physicist at England's Oxford University. [...] Amato Evan, a climate scientist at the University of Wisconsin, Madison, added that "the idea just isn't supported by the theory or by the observations."

• There is no reliable source claiming that Jupiter is warming. However, observations of the Red Spot Jr. storm suggest Jupiter could be in a period of global climate change. This is hypothesized to be part of an approximately 70 year global climate cycle, characterized by the relatively rapid forming and subsequent slow erosion and merging of cyclonic and anticyclonic vortices in Jupiter's atmosphere. These vortices facilitate the heat exchange between poles and equator. The cycle works like this: As the vortices erode, heat exchange is reduced; this makes the poles cool down and the equatorial region heat up; the resulting temperature difference destabilizes the atmosphere, leading to the creation of new vortices.

• Pluto has an extremely elliptical orbit with a period of about 248 years. It also is extremely far from earth, and hence any data is extremely sparse. There are conflicting measurements, but two data points from 1988 and 2002 seem to indicate that Pluto has indeed warmed between those two dates. Pluto's temperature is heavily influenced by its elliptical orbit - it was closest to the sun in 1989 and has slowly receeded since. If it has any thermal inertia, it is expected to warm for a while after it passes perihelion. No other mechanism has so far been seriously suggested. Here is a reasonable summary, and this paper discusses how the thermal inertia is provided by sublimation and evaporation of parts of Pluto's atmosphere. A more popular account is here and in Wikipedia's own excellent article.

  By the way, "temperature" is measured very indirectly in this case. When Pluto passes in front of a star, observers note how fast the light drops off. From this, they deduce the density of the atmosphere, and that is used as an indicator of temperature.

There was once a time when most scientists believed the earth was flat!

• No, there was not. Knowledge about the approximately spherical shape of the Earth was widespread among educated people long before the advent of modern science. Eratosthenes already gave a very good estimate for the diameter in 240 BC. Christopher Columbus was not laughed out of court because he believed the Earth was round, but because he assumed an unrealistically small diameter to make Asia reachable. See Flat Earth, which, among other goodies, has a sourced statement that "since the eighth century, no cosmographer worthy of note has called into question the sphericity of the Earth."

Can't the presently high levels of CO2 just be the result of temperature changes rather than fossil fuels, as they may have been in the past?

• While these claims are popular among global warming skeptics,[15][16][17] even some academically trained ones,[18] they are patently wrong. Over geological times, volcanic outgassing is responsible for a large part of atmospheric carbon dioxide. But current human emissions are at least 100 times larger than volcanic emission.[19] Volcano eruptions affect the climate in other ways, primarily by injecting aerosols into the atmosphere and thus exerting a (comparatively short term) cooling influence.[20] We know from isotopic analysis of atmospheric carbon dioxide that the observed increase is from fossil fuels, and cannot have come from volcanoes or the ocean. Release of carbon dioxide came from the oceans would also be associated with an increase in atmospheric oxygen content, since the same processes that cause oceanic outgassing of carbon dioxide would cause outgassing of other gases (such as oxygen). Instead we have measured a small decrease of atmospheric oxygen. And if the oceans were giving off some of their carbon dioxide, we would obviously expect a decrease in their carbon dioxide content. But instead we are measuring an increase in the oceans' carbon dioxide concentration, resulting in the oceans becoming more acidic (or more accurately, less basic).

Given that summer 2007 is so cold in (region X)...

• It's called "global warming", not "(region X) warming". Even then, what rises is the average temperature over time -- that is, the temperature will fluctuate up and down within the overall rising trend. In any case, what is tracked and reported is the "anomaly" that is, the change from normal over time, not absolute readings. If temperature goes up .5 degrees centigrade, it doesn't matter if that is added on to -10 or +10, it has still gone up .5

Weren't they saying in 1970 that pollution was going to freeze the world over by 2000?

• No: see global cooling

Isn't global warming "just a theory"?

• As is often the case, the term "global warming" is used with more than one meaning. That the temperature is rising is a fact. The explanation for this warming is a scientific theory. This is different from the common use of the word "theory" to mean a guess or supposition. A scientific theory is a coherent set of explanations that is compatible with the known observations, that allows predictions to be made, and that has a number of other properties (see the above linked article). A theory that makes a number of verifiable predictions that turn out to be correct gains credibility. Strictly speaking, science does not prove anything. A theory is the best it can provide.

What is the optimal temperature of the earth - and how do we know it's not 6 degrees warmer?

• There's no such thing as an "optimal" temperature of the earth. The nearest concept that is relevant is that there are ranges to which species and human society have adapted. Though it may not sound like much, a global temperature rise of 6 degrees is huge in climate terms. For example, the sea level rise it produced would flood coastal cities around the world.
• Earth climate has varied significantly over geological ages. The question of an "optimal temperature" makes no sense without a clear optimality criterion. Over geological time spans, ecosystems adapt to climate variations. But global climate variations during the development of human civilization (i.e., the past 12,000 years) have been remarkably small. Human civilization is highly adapted to the current stable climate. Agricultural production depends on the proper combination of soil, climate, methods, and seeds. Most large cities are located on the coast, and any significant change in sea level would strongly affect them. Migration of humans and ecosystems is limited by political borders and exisiting land use. In short, the main problem is not the absolute temperature, but the massive and unprecedentedly fast change in climate, and the second order-effects to human societies. The IPCC AR4 WG2 report has a detailed discussion of the effects of rapid climate change.

Aren’t climate variations inevitable with or without humans?

• Yes. Climate varies both with and without humans. But the current anthropogenic climate change is much faster than any known climate change in the past, giving ecosystems and human societies less time to adapt. It thus will have a stronger impact on ecosystems and human settlement than natural climate changes. However, this is only borderline related to the topic of this article. We have a fairly good understanding of the predominant causes for the current global warming, and know with good certainty that it is mostly caused by human action.

Since methane is a much more potent a greenhouse gas than CO2, why isn't it viewed as the culprit behind global warming?

• True, methane is more potent molecule for molecule. But there's far less of it in the atmosphere, so the total effect is smaller. One of the reasons for the lower concentration is that the atmospheric lifetime of methane is a lot shorter than that of CO2. Methane in the atmosphere decomposes into water and CO2. In other words, methane closely tracks current emissions, while CO2 accumulates in the atmosphere over long time periods. For details see the greenhouse gas and global warming potential articles.

References