| None like it hot
|Lies, talking points, manufactroversies|
|—Katharine Hayhoe, climatologist and evangelical Christian|
Global warming, also known as anthropogenic (or human-caused) global warming, is the rising average temperature of Earth's atmosphere and oceans and its related effects. In the last 100 years, Earth's average surface temperature increased by about 0.8 °C (1.4 °F) with about two thirds of the increase occurring over just the last three decades. As a result, anthropogenic global warming has recently become a major concern for humanity. Such concerns are supported worldwide by the wide majority of climatologists.
Global warming is an increase in temperature in addition to the natural greenhouse effect. The greenhouse effect interacts with other planet-wide influences such as the Milankovitch cycles in order to produce long term climate movements. Many gases contribute to the greenhouse effect, some of the most important being water vapor, methane and carbon dioxide. Black carbon (ie. soot) is third only to carbon dioxide and methane for its contribution to global warming, but it is the most effective at raising temperatures in the arctic by reducing the albedo.
 What's so bad about global warming?
Global warming is bad for a number of reasons.
- A dramatic rise in sea level. Global warming will cause a continuing sea level rise of an uncertain amount. The IPCC reports a range of 9 - 88 cm (3.5 - 34.6 inches) up to 2100, but further contributions are possible from glacier and ice sheet discharge from Greenland and Antarctica. Even this small rise would cause significant disruption to coastal communities. If the whole Greenland ice sheet melted this would lead to a global rise of 7 m (23 ft).
- More active weather systems. More energy in the atmosphere will lead to more active weather systems, with more frequent and more violent storms.
- Disturbed rainfall patterns. Rainfall patterns will be significantly disrupted, with floods in some places and droughts in others.
- Acidification of the oceans. Carbon dioxide dissolves in water by reacting to make H2CO3 (carbonic acid), causing great damage to fish stocks and coral reefs. Note this is not a consequence of warming: it is a consequence of the forcing agent, CO2. To make matters worse, this acidification appears to have been an important factor in the Permian-Triassic Extinction Event — the most severe extinction Earth has ever known — and possibly every extinction other than the Cretaceous.
- Tipping points/feedback loops. Multiple possibilities here. As glaciers disappear, the planet will not reflect as much solar radiation back into space, leading to more warming. When northern permafrost melts, the organic material will decompose and release methane, again leading to more warming. As the oceans warm, their ability to dissolve carbon dioxide decreases, and if ever reach a certain temperature, the methane stored under pressure on the seafloor will vaporize, leading to (you guessed it) more warming.
- Spread of tropical diseases. As northern latitudes become warmer, vectors that spread tropical diseases (such as mosquitoes or other organisms) will begin to encroach into new areas.
- Disruption of ocean currents. For example, the disruption of ocean currents could reduce the strength of the North Atlantic Drift that keeps Europe relatively warm for its latitude.
- Habitat loss or change faster than plants or animals can adapt. Mechanism such as species migration or changes in ecosystem boundaries often are slow, and in some cases could be slower than the speed of climate change. Some habitats may disappear completely: the loss of polar climates will leave animals such as polar bears cut off — or will have to actually breed with other local species.
- Loss of mountain glaciers and snowpack exacerbating summer droughts. Glaciers and snowpack act as natural reservoirs, for example releasing water that had fallen as snow several months later when summer arrives and snow melts. The loss of this natural storage mechanism will lead to floods in winter and droughts in the summer.
- And, if you've been sleeping through this list, serious damage to coffee, tea and chocolate stocks.
Not all of these consequences are certain, and some may be mitigated. For example, whilst global warming might tend to promote the spread of tropical diseases, advances in medicine or control measures (insect spraying, swamp draining) could well counteract this, as has already happened during the industrial era for a number of previously common diseases.
Equally though, there will probably be many unanticipated additional — probably negative — consequences.
If climate change doesn't sound so bad, consider that we've spent the past few hundred years building cities in places that don't flood, farms in places with enough water, and ice hotels in places with, well, ice. There is an awful lot of money and human endeavor relying on the weather staying just the way it is.
 What's the limit?
While projections of the potential (maximum) temperature rise have ranged from 2 - 6°C, there's broad agreement that anything above 2°C will mean we are beyond recovery. The International Energy Agency suggests that the window to prevent this from occurring will close by 2020, a view shared by the OECD. So let's get cracking.
 A reminder on comparing apples to apples
When comparing sources of greenhouse gases, be sure to note whether the figure lists the number of tons of carbon released, or the number of tons of carbon dioxide released. One ton of carbon dioxide contains only a little over a quarter ton of carbon.
 And what about that ozone thing?
Some members of the public get confused between ozone layer depletion and global warming - both involve some gases that somehow influence the already arcane dynamics of the atmosphere, and both are associated with dire consequences if we do not change our comfy lifestyle. There is a slight connection: Both ozone (O3) as well as the ozone killing CFCs act as greenhouse gases, but on a smaller scale than the usual suspects carbon dioxide (CO2) and methane (CH4)
However, they are largely separate issues: Ozone layer depletion means that we all die because the ozone layer vanishes and the surface of earth is bombarded with ultraviolet solar radiation, and global warming means that we face incredible hardship because the temperatures on earth rise too quickly for the ecosystems to adapt and the entire biosphere collapses.
 Global cooling?
Scientists noticed that historically, the world had been heading towards an ice age. A minority of scientists in the 1970's and earlier also predicted that the pollution would have cooling effect due to increased cloud cover from factories and other emissions. This actually is a thing and does throw a bit of a curveball into the models and appropriate course of action. For example, after 9/11 global air traffic more or less shut down, and the lack of contrails led to the discovery that airplane contrails act to stablize air temperature throughout the day. The real world is complicated[citation NOT needed], and people use science to discover how it works. As such, scientific knowledge marches ever forward, and obviously the world has been warming. But the few works published have been enough for "climate skeptics" to strip mine for quotes.
 See also
- Global warming denialism
- Global warming conspiracy theory
- Renewable energy
- Kyoto Protocol
- The global warming wager
- Gore's Law
- Evidence for Climate Change is Overwhelming, RAND Corporation
- Four Ways to Look at Global Carbon Footprints, National Geographic
- By all means question climate policies. But facts are facts, The Economist
- Shattering Myths to Help the Climate, The New York Times
- What climate scientists should talk about: their personal stories, Skeptical Science (See also 97 Hours of Consensus)
- Which countries are decarbonizing the fastest?, Vox
- IEA Shows How to Radically Reduce CO2, Climate Central
- ↑ Missionary from Toronto winning converts — on climate change, University of Toronto
- ↑ Black carbon ranks as second-biggest human cause of global warming, Washington Post
- ↑ Peter D. Ward. Under a Green Sky (2007) 
- ↑ Unusual number of grizzly and hybrid bears spotted in High Arctic, Yale University
- ↑ Climate change makes waking up to smell the coffee more expensive, NASA
- ↑ Tea industry's future depends on corporate collaboration, BBC
- ↑ Climate Change Could Melt Chocolate Production, Scientific American
- ↑ Limiting Global Warming to 2°C: Can Europe and the United States Keep the Climate Window Open?, German Marshall Fund
- ↑ The climate challenge: Achieving zero emissions, OECD
- ↑ CDIAC list of greenhouse gases
- ↑ IPCC list of greenhouse gases
- ↑ Impacts of water, carbon dioxide, methane and ozone on the overall greenhouse effect, See also  for a summary
- ↑ Technically speaking we are still in one as we still have permanent polar ice caps, for now, but towards the type of ice age where most of the world looks like Alaska.
- ↑ From NOVA, "Are vapor trails from air traffic influencing the climate?"