Talk:Climate change

A1: Yes. The IPCC findings of recent warming as a result of human influence are explicitly recognized as the "consensus" scientific view by the science academies of all the major industrialized countries. No scientific body of national or international standing presently rejects the basic findings of human influence on recent climate. This scientific consensus is supported by over 99% of publishing climate scientists.^[1]

A2: This is why it is termed "global warming", not "(such-and-such a place) 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. To give an idea of the relevant time scales, the standard averaging period specified by the World Meteorological Organisation (WMO) is 30 years. Accordingly, the WMO defines climate change as "a statistically significant variation in either the mean state of the climate or in its variability, persisting for an extended period (typically decades or longer)."^[2]

A3: While these claims are popular among global warming skeptics,^[3][4] including academically trained ones,^[5][6] they are incorrect. This is known from any of several perspectives:

• Current human emissions of CO₂ are at least 100 times larger than volcanic emissions. Measurements of CO₂ levels over the past 50 years do not show any significant rises after eruptions.^[7] This is easily seen in a graph of CO₂ concentrations over the past 50 years: the strongest eruption during the period, that of Mount Pinatubo in 1991, produced no increase in the trend.
• Isotopic analysis of atmospheric carbon dioxide shows the observed change in the ratio of carbon isotopes reflects the isotopic ratios in fossil fuels.^[8]
• Atmospheric oxygen content is decreasing at a rate that agrees with the amount of oxygen being used to burn fossil fuels.^[9]
• If the oceans were giving up some of their carbon dioxide, their carbon dioxide concentration would have to decrease. But instead we are measuring an increase in the oceans' carbon dioxide concentration, resulting in the oceans becoming more acidic (or in other words, less basic).^[10]

A4: Yes. Keep in mind that your points need to be based on documented evidence from the peer-reviewed literature, or other information that meets standards of verifiability, reliability, and no original research. If you do not have such evidence, more experienced editors may be able to help you find it (or confirm that such evidence does not exist). You are welcome to make such queries on the article's talk page but please keep in mind that the talk page is for discussing improvements to the article, not discussing the topic. There are many forums that welcome general discussions of global warming, but the article talk page is not such a forum.

A5: Two reasons:

• There are many images used in the articles related to global warming, and there are many reasons why they may not be updated with the latest data. Some of the figures, like the Global Warming Map, are static, meaning that they are intended to show a particular phenomenon and are not meant to be updated frequently or at all. Others, like the Instrumental Temperature Record and Northern Hemisphere Sea Ice Extent Anomalies, use yearly data and thus are updated once per year—usually in mid- to late-January, depending upon when the data is publicly released, and when a volunteer creates the image. Still others, like Mauna Loa Carbon Dioxide, use monthly data. These are updated semi-regularly.
• However, just because an image is 6 months or a year old does not mean it is useless. Robert A. Heinlein is credited with saying, "Climate is what you expect, weather is what you get", meaning that climate is defined as a long-term average of weather, usually about 30 years. This length was chosen to eliminate the year-to-year variations.^[11] Thus, in terms of climate change, any given year's data is of little import.

A6: People who say this are abusing the word "theory" by conflating its common meaning with its scientific meaning. In common usage, "theory" can mean a hunch or guess, but a scientific theory, roughly speaking, means a coherent set of explanations that is compatible with observations and that allows predictions to be made. That the temperature is rising is an observation. An explanation for this (also known as a hypothesis) is that the warming is primarily driven by greenhouse gases (such as CO₂ and methane) released into the atmosphere by human activity. Scientific models have been built that predict the rise in temperature and these predictions have matched observations. When scientists gain confidence in a hypothesis because it matches observation and has survived intense scrutiny, the hypothesis may be called a "theory". Strictly speaking, scientific theories are never proven, but the degree of confidence in a theory can be discussed. The scientific models now suggest that it is "extremely likely" (>95%) to "virtually certain" (>99%) that the increases in temperature have been caused by human activity as discussed in the IPCC Fifth Assessment Report. Global warming via greenhouse gases by human activity is a theory (in the scientific sense), but it is most definitely not just a hunch or guess.

A7: It's true that methane is more potent molecule for molecule. But there's far less of it in the atmosphere, so the total effect is smaller. The atmospheric lifetime of methane (about 10 years) is a lot shorter than that of CO₂ (hundreds to thousands of years), so when methane emissions are reduced the concentration in the atmosphere soon falls, whereas CO₂ accumulates in the atmosphere over long periods. For details see the greenhouse gas and global warming potential articles.

A8: Consensus is not the same as unanimity, the latter of which is impractical for large groups. Over 99% of publishing climate scientists agree on anthropogenic climate change.^[1] This is an extremely high percentage well past any reasonable threshold for consensus. Any list of "skeptical scientists" would be dwarfed by a comparably compiled list of scientists accepting anthropogenic climate change.

A9: One of the strongest El Niño events in the instrumental record occurred during late 1997 through 1998, causing a spike in global temperature for 1998. Through the mid-late 2000s this abnormally warm year could be chosen as the starting point for comparisons with later years in order to produce a cooling trend; choosing any other year in the 20th century produced a warming trend. This no longer holds since the mean global temperatures in 2005, 2010, 2014, 2015 and 2016 have all been warmer than 1998.^[12] More importantly, scientists do not define a "trend" by looking at the difference between two given years. Instead they use methods such as linear regression that take into account all the values in a series of data. The World Meteorological Organisation specifies 30 years as the standard averaging period for climate statistics so that year-to-year fluctuations are averaged out;^[2] thus, 10 years isn't long enough to detect a climate trend.

A10: Some people assume this because of the island's name. In fact the Saga of Erik the Red tells us Erik named the new colony Greenland because "men will desire much the more to go there if the land has a good name."^[13] Advertising hype was alive and well in 985 AD.

While much of Greenland was and remains under a large ice sheet, the areas of Greenland that were settled by the Norse were coastal areas with fjords that, to this day, remain quite green. You can see the following images for reference:

• A map of the Eastern Settlement
• A satellite image of that area today
• A map of the Western Settlement
• A satellite image of that area today
• A zoom in on the general area where the Brattahlíð (Erik the Red's farm) and Garðar farms were located

A11: The IPCC reports are not produced by "UN scientists". The IPCC does not employ the scientists who generate the reports, and it has no control over them. The scientists are internationally recognized experts, most with a long history of successful research in the field. They are employed by various 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.

A12: Measurements show that it has not.^[14] Claims that global sea ice amounts have stayed the same or increased are a result of cherry picking two data points to compare, while ignoring the real (strongly statistically significant) downward trend in measurements of global sea ice amounts.

Arctic sea ice cover is declining strongly; Antarctic sea ice cover has had some much smaller increases, though it may or may not be thinning, and the Southern Ocean is warming. The net global ice-cover trend is clearly downwards.

A13: They weren't – see the article on global cooling. An article in the Bulletin of the American Meteorological Society has reviewed the scientific literature at that time and found that even during the 1970s the prevailing scientific concern was over warming.^[15] The common misperception that cooling was the main concern during the 1970s arose from a few studies that were sensationalized in the popular press, such as a short nine-paragraph article that appeared in Newsweek in 1975.^[16] (Newsweek eventually apologized for having misrepresented the state of the science in the 1970s.)^[17] The author of that article has repudiated the idea that it should be used to deny global warming.^[18]

A14: Water vapour is indeed a major greenhouse gas, contributing about 36% to 70% (not 98%) of the total greenhouse effect. But water vapour has a very short atmospheric lifetime (about 10 days), compared with decades to centuries for greenhouse gases like CO₂ or nitrous oxide. As a result it is very nearly in a dynamic equilibrium in the atmosphere, which globally maintains a nearly constant relative humidity. In simpler terms, any excess water vapour is removed by rainfall, and any deficit of water vapour is replenished by evaporation from the Earth's surface, which literally has oceans of water. Thus water vapour cannot act as a driver of climate change.

Rising temperatures caused by the long-lived greenhouse gases will however allow the atmosphere to hold more vapour. This will lead to an increase in the absolute amount of water vapour in the atmosphere. Since water vapour is itself a greenhouse gas, this is an example of a positive feedback. Thus, whereas water vapour is not a driver of climate change, it amplifies existing trends.

A15: While some solar system bodies show evidence of local or global climate change, there is no evidence for a common cause of warming.

• 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.^[19] Abdussamatov's views have no support in the scientific community, as the second page of the National Geographic article makes 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.'"^[20]
• 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.^[21][22] 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 that help transfer heat between Jupiter's 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.^[23][24]
• Pluto has an extremely elliptical orbit with a period of about 248 years. Data are sparse, but two data points from 1988 and 2002 indirectly suggest that Pluto warmed between those two dates.^[25] Pluto's temperature is heavily influenced by its elliptical orbit – it was closest to the sun in 1989 and has slowly receded since. Because of thermal inertia, it is expected to warm for a while after it passes perihelion (similar to how a sunny day's warmest temperatures happen during the afternoon instead of right at noon). 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 article.

A16: No,

• Scientists participate in international organizations like the IPCC as part of their normal academic duties. They do not receive any extra compensation beyond possibly for direct expenses.
• Scientific grants do not usually award any money to a scientist personally, only towards the cost of his or her scientific work.
• There is not a shortage of useful things that scientists could study if they were not studying global warming.
  • Understanding our climate system better brings benefits independent of global warming. For instance, more accurate weather predictions save a lot of money (on the order of billions of dollars a year), and everyone from insurance agents to farmers wants climate data.^[26][27] Scientists could get paid to study climate even if global warming did not exist.

A17: It does, but the fact that natural variation occurs does not mean that human-induced change cannot also occur. Climate scientists have extensively studied natural causes of climate change (such as orbital changes, volcanism, and solar variation) and have ruled them out as an explanation for the current temperature increase. Human activity is the cause at the 95 to 99 percent confidence level (see the IPCC Fifth Assessment Report for details). The high level of certainty in this is important to keep in mind to spot mention of natural variation functioning as a distraction.

A18: This page is about the science of climate change. It doesn't talk about planetary doom or catastrophe. For a technical explanation, see catastrophic climate change, and for paleoclimatic examples see PETM and great dying.

A19: Though it may not sound like much, a global temperature rise of 3 degrees Celsius (5.4 degrees Fahrenheit) is huge in climate terms. For example, the sea level rise it would produce would flood coastal cities around the world, which include most large cities.

• Earth's 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 existing land use. In short, the main problem is not the higher absolute temperature but the massive and unprecedentedly fast change in climate and the related effects on human societies. The IPCC AR6 WG2 report has a detailed discussion of the effects of rapid climate change.

A20: Scibaby is/was a long term abusive sock-master (or coordinated group of sock masters) who has created 1,027 confirmed sock puppets, another 167 suspected socks, and probably many untagged or unrecognized ones. This page lists some recent creations. His modus operandi has changed over time, but includes proposing reasonably worded additions on the talk page that only on close examination turn out to be irrelevant, misinterpreted, or give undue weight to certain aspects. Scibaby is banned, and Scibaby socks are blocked as soon as they are identified. Some editors silently revert his additions, per WP:DENY, while others still assume good faith even for likely socks and engage them.

A21: There are hundreds of peer-reviewed papers published every month in respected scientific journals such as Geophysical Research Letters, the Journal of Climate, and others. We can't include all of them, but the article does include references to individual papers where there is consensus that they best represent the state of the relevant science. This is in accordance with the "due weight" principle (WP:WEIGHT) of the Neutral point of view policy and the "Wikipedia is not an indiscriminate collection of information" principle (WP:IINFO) of the What Wikipedia is not policy.

A22: Yes, the planet has warmed and cooled before. However, the term "climate change" without further qualification is widely understood to refer to the recent episode and often explicitly connected with the greenhouse effect. Per WP:COMMONNAME, we use the term in this most common meaning. The article Climate variability and change deals with the more general concept.

A23: No. For cosmic rays to be causing global warming, all of the following would have to be true, whereas only the italicized one was tested in the 2011 experiment:^[28]

• Solar magnetic field must be getting stronger
• The number of cosmic rays reaching Earth must be dropping
• Cosmic rays must successfully seed clouds, which requires:

1. Cosmic rays must trigger aerosol (liquid droplet) formation,
2. These newly-formed aerosols must grow sufficiently through condensation to form cloud-condensation nuclei (CCN),
3. The CCN must lead to increased cloud formation, and
4. Cloud cover on Earth must be declining.

Perhaps the study's lead author, Jasper Kirkby, put it best: "...it [the experiment] actually says nothing about a possible cosmic-ray effect on clouds and climate, but it's a very important first step."^[29]

A24: Yes, this is true for all plausible single things including: "electric cars", "planting trees", "low-carbon technology", "renewable energy", "Australia", "capitalism", "the doom & gloom approach", "a Ph.D. in thermodynamics". Note that it is problematic to use the word "fix" regarding climate change, as returning the climate to its pre-industrial state currently appears to be feasible only over a timeframe of thousands of years. Current efforts are instead aimed at mitigating (meaning limiting) climate change. Mitigation is strived for through the combination of many different things. See Climate change mitigation for details.