Shutdown of thermohaline circulation

A shutdown or slowdown of the thermohaline circulation is an effect of global warming on a major ocean circulation.

Data from NASA in 2010 suggested that the Atlantic Meridional Overturning Circulation (AMOC) had not slowed down, but may have actually sped up slightly since 1993.[1] A 2015 study suggested that the AMOC has weakened by 15-20% in 200 years.[2]

Thermohaline Circulation 2
A summary of the path of the thermohaline circulation. Blue paths represent deep-water currents, while red paths represent surface currents


Don Chambers from the University of South Florida College of Marine Science mentioned, "The major effect of a slowing AMOC is expected to be cooler winters and summers around the North Atlantic, and small regional increases in sea level on the North American coast."[3] James Hansen and Makiko Sato stated,

AMOC slowdown that causes cooling ~1°C and perhaps affects weather patterns is very different from an AMOC shutdown that cools the North Atlantic several degrees Celsius; the latter would have dramatic effects on storms and be irreversible on the century time scale.[4]

Downturn of the Atlantic meridional overturning circulation, has been tied to extreme regional sea level rise.[5]

A 2017 review concluded that there is strong evidence for past changes in the strength and structure of the AMOC during abrupt climate events such as the Younger Dryas and many of the Heinrich events.[6]


Lohmann and Dima 2010 found a weakening of the AMOC since the late 1930s.[7] Climate scientists Michael Mann of Penn State and Stefan Rahmstorf from the Potsdam Institute for Climate Impact Research suggested that the observed cold pattern during years of temperature records is a sign that the Atlantic Ocean's Meridional overturning circulation (AMOC) may be weakening. They published their findings in 2015, and concluded that the AMOC circulation showed exceptional slowdown in the last century, and that Greenland melt is a possible contributor, with the slowdown of AMOC since the 1970s being unprecedented over the last millennium.[8]

A study published in 2016 found further evidence for a considerable impact from sea level rise for the U.S. East Coast. The study confirms earlier research findings which identified the region as a hotspot for rising seas, with a potential to divert 3–4 times in the rate of rise, compared to the global average. The researchers attribute the possible increase to an ocean circulation mechanism called deep water formation, which is reduced due to AMOC slow down, leading to more warmer water pockets below the surface. Additionally, the study noted, "Our results suggest that higher carbon emission rates also contribute to increased [sea level rise] in this region compared to the global average."[9]


Global warming could, via a shutdown of the thermohaline circulation, trigger cooling in the North Atlantic, Europe, and North America.[10][11] This would particularly affect areas such as the British Isles, France and the Nordic countries, which are warmed by the North Atlantic drift.[12][13] Major consequences, apart from regional cooling, could also include an increase in major floods and storms, a collapse of plankton stocks, warming or rainfall changes in the tropics or Alaska and Antarctica, more frequent and intense El Niño events due to associated shutdowns of the Kuroshio, Leeuwin, and East Australian Currents that are connected to the same thermohaline circulation as the Gulf Stream, or an oceanic anoxic eventoxygen (O
below surface levels of the stagnant oceans becomes completely depleted — a probable cause of past mass extinction events.[14]

Effects on weather

Hansen et al. 2015 found, that the shutdown or substantial slowdown of the AMOC, besides possibly contributing to extreme end-Eemian events, will cause a more general increase of severe weather. Additional surface cooling from ice melt increases surface and lower tropospheric temperature gradients, and causes in model simulations a large increase of mid-latitude eddy energy throughout the midlatitude troposphere. This in turn leads to an increase of baroclinicity produced by stronger temperature gradients, which provides energy for more severe weather events.

Many of the most memorable and devastating storms in eastern North America and western Europe, popularly known as superstorms, have been winter cyclonic storms, though sometimes occurring in late fall or early spring, that generate near-hurricane-force winds and often large amounts of snowfall. Continued warming of low latitude oceans in coming decades will provide more water vapor to strengthen such storms. If this tropical warming is combined with a cooler North Atlantic Ocean from AMOC slowdown and an increase in midlatitude eddy energy, we can anticipate more severe baroclinic storms.

Hansen et al. results at least imply that strong cooling in the North Atlantic from AMOC shutdown does create higher wind speed. The increment in seasonal mean wind speed of the northeasterlies relative to preindustrial conditions is as much as 10–20 %. Such a percentage increase of wind speed in a storm translates into an increase of storm power dissipation by a factor ∼1.4–2, because wind power dissipation is proportional to the cube of wind speed. However, the simulated changes refer to seasonal mean winds averaged over large grid-boxes, not individual storms.[15]


2010 and earlier

In April 2004, the hypothesis that the Gulf Stream is switching off received a boost when a retrospective analysis of U.S. satellite data seemed to show a slowing of the North Atlantic Gyre, the northern swirl of the Gulf Stream.[16]

In May 2005, Peter Wadhams reported in The Times (London) about the results of investigations in a submarine under the Arctic ice sheet measuring the giant chimneys of cold dense water, in which the cold dense water normally sinks down to the sea bed and is replaced by warm water, forming one of the engines of the North Atlantic Drift. He and his team found the chimneys to have virtually disappeared. Normally there are seven to twelve giant columns, but Wadhams found only two giant columns, both extremely weak.[17][18]

In 2005 a 30% reduction in the warm currents that carry water north from the Gulf Stream was observed, from the last such measurement in 1992. The authors noted uncertainties in the measurements.[19] Following media discussions, Detlef Quadfasel pointed out that the uncertainty of the estimates of Bryden et al. is high, but says other factors and observations do support their results, and implications based on palaeoclimate records show drops of air temperature up to 10 °C within decades, linked to abrupt switches of ocean circulation when a certain threshold is reached. He concluded that further observations and modelling are crucial for providing early warning of a possible devastating breakdown of the circulation.[20] In response Quirin Schiermeier concluded that natural variation was the culprit for the observations but highlighted possible implications.[14][21]

In 2008, Vage et al. reported "the return of deep convection to the subpolar gyre in both the Labrador and Irminger seas in the winter of 2007–2008," employing "profiling float data from the Argo program to document deep mixing," and "a variety of in situ, satellite and reanalysis data" to set the context for the phenomenon. This might have a lot to do with the observations of variations in cold water chimney behaviour.[22]

In January 2010, the Gulf Stream briefly connected with the West Greenland Current after fluctuating for a few weeks due to an extreme negative phase of the Arctic oscillation, temporarily diverting it west of Greenland.[23][24]

Thermohaline circulation and fresh water

95307main fig4m
The red end of the spectrum indicates slowing in this presentation of the trend of velocities derived from NASA Pathfinder altimeter data from May 1992 to June 2002. Source: NASA.

Heat is transported from the equator polewards mostly by the atmosphere but also by ocean currents, with warm water near the surface and cold water at deeper levels. The best known segment of this circulation is the Gulf Stream, a wind-driven gyre, which transports warm water from the Caribbean northwards. A northwards branch of the Gulf Stream, the North Atlantic Drift, is part of the thermohaline circulation (THC), transporting warmth further north to the North Atlantic, where its effect in warming the atmosphere contributes to warming Europe.

The evaporation of ocean water in the North Atlantic increases the salinity of the water as well as cooling it, both actions increasing the density of water at the surface. Formation of sea ice further increases the salinity and density, because salt is ejected into the ocean when sea ice forms.[25] This dense water then sinks and the circulation stream continues in a southerly direction. However, the Atlantic Meridional Overturning Circulation (AMOC) is driven by ocean temperature and salinity differences. But freshwater decreases ocean water salinity, and through this process prevents colder waters sinking. This mechanism possibly caused the cold ocean surface temperature anomaly currently observed near Greenland (Cold blob (North Atlantic)).[26]

Global warming could lead to an increase in freshwater in the northern oceans, by melting glaciers in Greenland, and by increasing precipitation, especially through Siberian rivers.[27][28]

An AMOC shutdown may be able to trigger the type of abrupt massive temperature shifts which occurred during the last glacial period: a series of Dansgaard-Oeschger events – rapid climate fluctuations – may be attributed to freshwater forcing at high latitude interrupting the THC. 2002 model runs in which the THC is forced to shut down do show cooling – locally up to 8 °C (14 °F).[29]

Studies of the Florida Current suggest that the Gulf Stream weakens with cooling, being weakest (by ~10%) during the Little Ice Age.[30]

Subpolar gyre

Recent studies (2017) suggest potential convection collapse (heat transport) of the subpolar gyre in the North Atlantic, resulting in rapid cooling, with implications for economic sectors, agriculture industry, water resources and energy management in Western Europe and the East Coast of the United States.[31] Frajka-Williams et al. 2017 pointed out that recent changes in cooling of the subpolar gyre, warm temperatures in the subtropics and cool anomalies over the tropics, increased the spatial distribution of meridional gradient in sea surface temperatures, which is not captured by the AMO Index.[32]

IPCC models

Based on coupled Atmosphere-Ocean General Circulation Models from 2001, the THC tends to weaken somewhat rather than stop, and the warming effects outweigh the cooling, even over Europe.[33] In the IPCC Fifth Assessment Report, it was reported that it is very unlikely that the AMOC will undergo a rapid transition (high confidence).[34]

In popular culture

The film The Day After Tomorrow exaggerates a scenario related to the AMOC shutdown.

See also


  1. ^ "NASA - NASA Study Finds Atlantic 'Conveyor Belt' Not Slowing". National Aeronautics and Space Administration. 25 March 2010. Retrieved 3 September 2017.
  2. ^ Rahmstorf, Stefan; Box, Jason E.; Feulner, Georg; Mann, Michael E.; Robinson, Alexander; Rutherford, Scott; Schaffernicht, Erik J. (2015). "Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation". Nature Climate Change. 5 (5): 475–480. Bibcode:2015NatCC...5..475R. doi:10.1038/nclimate2554. ISSN 1758-678X. closed access publication – behind paywall PDF in UNEP Document Repository
  3. ^ "Melting Greenland ice sheet may affect global ocean circulation, future climate". 2016.
  4. ^ James Hansen; Makiko Sato (2015). "Predictions Implicit in "Ice Melt" Paper and Global Implications".
  5. ^ Jianjun Yin & Stephen Griffies (25 March 2015). "Extreme sea level rise event linked to AMOC downturn". CLIVAR.
  6. ^ Jean Lynch-Stieglitz (2017). "The Atlantic Meridional Overturning Circulation and Abrupt Climate Change". Annual Review of Marine Science. Bibcode:2017ARMS....9...83L. doi:10.1146/annurev-marine-010816-060415.
  7. ^ Mihai Dima; Gerrit Lohmann (2010). "Evidence for Two Distinct Modes of Large-Scale Ocean Circulation Changes over the Last Century". AMS. 23 (1): 5–16. Bibcode:2010JCli...23....5D. doi:10.1175/2009JCLI2867.1.
  8. ^ Stefan Rahmstorf; Jason E. Box; Georg Feulner; Michael E. Mann; Alexander Robinson; Scott Rutherford; Erik J. Schaffernicht (2015). "Exceptional twentieth-century slowdown in Atlantic Ocean overturning circulation". Nature. 5 (5): 475–480. Bibcode:2015NatCC...5..475R. doi:10.1038/nclimate2554.
  9. ^ "Why the U.S. East Coast could be a major 'hotspot' for rising seas". The Washington Post. 2016.
  10. ^ Shutdown Of Circulation Pattern Could Be Disastrous, Researchers Say, December 20, 2004, ScienceDaily
  11. ^ "Possible Economic Impacts of a Shutdown of the Thermohaline Circulation: an Application of FUND". CiteSeerX
  12. ^ "Weather Facts: North Atlantic Drift (Gulf Stream) - Weather UK -".
  13. ^ "The North Atlantic Drift Current".
  14. ^ a b Schiermeier, Quirin (2007). "Ocean circulation noisy, not stalling". Nature. 448 (7156): 844–5. Bibcode:2007Natur.448..844S. doi:10.1038/448844b. PMID 17713489.
  15. ^ J. Hansen, M. Sato, P. Hearty, R. Ruedy, M. Kelley, V. Masson-Delmotte, G. Russell, G. Tselioudis, J. Cao, E. Rignot, I. Velicogna, E. Kandiano, K. von Schuckmann, P. Kharecha, A. N. Legrande, M. Bauer, and K.-W. Lo (2015). "Ice melt, sea level rise and superstorms: evidence from paleoclimate data, climate modeling, and modern observations that 2 °C global warming is highly dangerous". Atmospheric Chemistry and Physics Discussions. 15 (14): 20059–20179. Bibcode:2015ACPD...1520059H. doi:10.5194/acpd-15-20059-2015.CS1 maint: Multiple names: authors list (link)
  16. ^ Satellites record weakening North Atlantic Current. NASA, 15 April 2004.
  17. ^ Leake, Jonathan (8 May 2005). "Britain faces big chill as ocean current slows". The Sunday Times.
  18. ^ Gulf Stream slowdown?, 26 May 2005.
  19. ^ F. Pearce. Failing ocean current raises fears of mini ice age. NewScientist, 30 November 2005
  20. ^ Quadfasel D (December 2005). "Oceanography: The Atlantic heat conveyor slows". Nature. 438 (7068): 565–6. Bibcode:2005Natur.438..565Q. doi:10.1038/438565a. PMID 16319866.
  21. ^ Schiermeier, Quirin (2007). "Climate change: A sea change". Nature. 439 (7074): 256–60. Bibcode:2006Natur.439..256S. doi:10.1038/439256a. PMID 16421539. (subscription required); see also "Atlantic circulation change summary". 19 Jan 2006.
  22. ^ Våge, Kjetil; Pickart, Robert S.; Thierry, Virginie; Reverdin, Gilles; Lee, Craig M.; Petrie, Brian; Agnew, Tom A.; Wong, Amy; Ribergaard, Mads H. (2009). "Surprising return of deep convection to the subpolar North Atlantic Ocean in winter 2007–2008". Nature Geoscience. 2 (1): 67–72. Bibcode:2009NatGe...2...67V. doi:10.1038/ngeo382.
  23. ^ FishOutofWater, Diaries (6 January 2010). "Freak Current Takes Gulf Stream to Greenland". Daily Kos. Retrieved 11 January 2010.
  24. ^ FishOutofWater, Diaries (30 December 2009). "Warm Atlantic Water Rapidly Replacing Arctic Sea Ice". Daily Kos. Retrieved 11 January 2010.
  25. ^ "Salinity and Brine". NSIDC.
  26. ^ "Everything you need to know about the surprisingly cold 'blob' in the North Atlantic ocean". The Washington Post. 2015.
  27. ^ Gierz, Paul (31 August 2015). "Response of Atlantic Overturning to future warming in a coupled atmosphere-ocean-ice sheet model". Geophysical Research Letters. 42 (16): 6811–6818. Bibcode:2015GeoRL..42.6811G. doi:10.1002/2015GL065276.
  28. ^ Turrell, B. The Big Chill Transcript of discussion on BBC 2, 13 November 2003
  29. ^ Vellinga, M.; Wood, R.A. (2002). "Global climatic impacts of a collapse of the Atlantic thermohaline circulation" (PDF). Climatic Change. 54 (3): 251–267. doi:10.1023/A:1016168827653. Archived from the original (PDF) on 6 September 2006.
  30. ^ Lund DC, Lynch-Stieglitz J, Curry WB; Lynch-Stieglitz; Curry (November 2006). "Gulf Stream density structure and transport during the past millennium". Nature. 444 (7119): 601–4. Bibcode:2006Natur.444..601L. doi:10.1038/nature05277. PMID 17136090.CS1 maint: Multiple names: authors list (link)
  31. ^ Sgubin; et al. (2017). "Abrupt cooling over the North Atlantic in modern climate models". Nature Communications. 8. Bibcode:2017NatCo...8.....S. doi:10.1038/ncomms14375. PMC 5330854. PMID 28198383.
  32. ^ Eleanor Frajka-Williams; Claudie Beaulieu; Aurelie Duchez (2017). "Emerging negative Atlantic Multidecadal Oscillation index in spite of warm subtropics". Scientific Reports. 7: 11224. Bibcode:2017NatSR...711224F. doi:10.1038/s41598-017-11046-x. PMID 28894211.
  33. ^ IPCC TAR WG1 (2001). " Thermohaline circulation changes". In Houghton, J.T.; Ding, Y.; Griggs, D.J.; Noguer, M.; van der Linden, P.J.; Dai, X.; Maskell, K.; Johnson, C.A. Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third Assessment Report of the Intergovernmental Panel on Climate Change. Cambridge University Press. ISBN 978-0-521-80767-8. Archived from the original on 30 March 2016 (pb: 0-521-01495-6)
  34. ^ "IPCC AR5 WG1" (PDF). IPCC. IPCC. p. Table 12.4. Archived from the original (PDF) on 24 August 2015.

External links

2014 United Nations Climate Change Conference

The United Nations Climate Change Conference, COP20 or CMP10 was held in Lima, Peru, from December 1 to 12, 2014. This was the 20th yearly session of the Conference of the Parties (COP 20) to the 1992 United Nations Framework Convention on Climate Change (UNFCCC) and the 10th session of the Meeting of the Parties (CMP 10) to the 1997 Kyoto Protocol. The conference delegates held negotiations towards a global climate agreement.

Abyss Box

The Abyss Box is a vessel containing 16 litres (3.5 imp gal; 4.2 US gal) of water at the very high pressure of 18 megapascal to simulate the natural underwater environment of hadal fauna living at about 1,800 metres (5,900 ft) below the surface. It is on display at Oceanopolis aquarium in Brest, France. It was designed by French researcher Bruce Shillito from Pierre and Marie Curie University in Paris.All the equipment maintaining the extreme pressure inside the Abyss Box weighs 600 kilograms (1,300 lb). The device will keep deep-dwelling creatures alive so they can be studied, especially regarding their adaptability to warmer ocean temperatures. Currently the Abyss Box houses only common species of deep sea creatures including a deep sea crab, Bythograea thermydron and a deep sea prawn, Pandalus borealis, which are some of the hardier species with a higher survival rate in depressurized environments.

Climate change in Japan

Climate change in Japan is being addressed at a governmental level.

The Intergovernmental Panel on Climate Change (IPCC) proposes two hypothetical future scenarios. One is Scenario "A1B" based on the assumption that a future world will have more global economic growth (the concentration of carbon dioxide will be 720ppm in 2100). The other is Scenario "B1" based on the assumption that a future world will have global green economy (the concentration of carbon dioxide will be 550ppm in 2100).

Earth Simulator calculations reveal the daily increase in mean temperature in Japan during the period of 2071 to 2100. The temperature will increased by 3.0 °C in Scenario B1 and 4.2 °C in A1B compared to that of 1971 to 2000. Similarly, the daily maximum temperature in Japan will increase by 3.1 °C in B1 and 4.4 °C in A1B. The precipitation in summer in Japan will increase steadily due to global warming (annual average precipitation will increase by 17% in Scenario B1 and by 19% in Scenario A1B during the period of 2071 to 2100 compared to that of 1971 to 2000).Currently, Japan is a world leader in the development of new climate-friendly technologies. Honda and Toyota hybrid electric vehicles were named to have the highest fuel efficiency and lowest emissions. The fuel economy and emissions decrease is due to the advanced technology in hybrid systems, biofuels, use of lighter weight material and better engineering.

As a signatory of the Kyoto Protocol, and host of the 1997 conference which created it, Japan is under treaty obligations to reduce its carbon dioxide emissions and to take other steps related to curbing climate change. The Cool Biz campaign introduced under former Prime Minister Junichiro Koizumi was targeted at reducing energy use through the reduction of air conditioning use in government offices.

Climate justice

Climate justice is a term used for framing global warming as an ethical and political issue, rather than one that is purely environmental or physical in nature. This is done by relating the effects of climate change to concepts of justice, particularly environmental justice and social justice and by examining issues such as equality, human rights, collective rights, and the historical responsibilities for climate change. A fundamental proposition of climate justice is that those who are least responsible for climate change suffer its gravest consequences.The term climate justice is also used to mean actual legal action on climate change issues. In 2017, a report of the United Nations Environment Programme identified 894 ongoing legal actions worldwide. At the end of 2018, a series of school strikes for climate started worldwide, inspired by Greta Thunberg's original protest in Sweden.

Forest dieback

Forest dieback (also "Waldsterben", a German loan word) is a condition in trees or woody plants in which peripheral parts are killed, either by pathogens, parasites or due to conditions like acid rain and drought. Two of the nine tipping points for major climate changes, forecast for the next century, are directly related to forest diebacks.

Global cooling

Global cooling was a conjecture during the 1970s of imminent cooling of the Earth's surface and atmosphere culminating in a period of extensive glaciation.

Press reports at the time did not accurately reflect the full scope of the debate in the scientific literature. The current scientific opinion on climate change is that the Earth underwent global warming throughout the 20th century and continues to warm.

Global warming in popular culture

The issue of global warming, its possible effects, and related human-environment interaction have entered popular culture since the late 20th century.

Science historian Naomi Oreskes has noted, "There's a huge disconnect between what professional scientists have studied and learned in the last 30 years, and what is out there in the popular culture." An academic study contrasts the relatively rapid acceptance of ozone depletion as reflected in popular culture with the much slower acceptance of the scientific consensus on global warming.

Greenhouse effect

The greenhouse effect is the process by which radiation from a planet's atmosphere warms the planet's surface to a temperature above what it would be without its atmosphere.If a planet's atmosphere contains radiatively active gases (i.e., greenhouse gases) they will radiate energy in all directions. Part of this radiation is directed towards the surface, warming it.

The intensity of the downward radiation – that is, the strength of the greenhouse effect – will depend on the atmosphere's temperature and on the amount of greenhouse gases that the atmosphere contains.

Earth’s natural greenhouse effect is critical to supporting life. Human activities, mainly the burning of fossil fuels and clearing of forests, have strengthened the greenhouse effect and caused global warming.The term "greenhouse effect" is a misnomer that arose from a faulty analogy with the effect of sunlight passing through glass and warming a greenhouse. The way a greenhouse retains heat is fundamentally different, as a greenhouse works mostly by reducing airflow so that warm air is kept inside.

Greenland Sea

The Greenland Sea is a body of water that borders Greenland to the west, the Svalbard archipelago to the east, Fram Strait and the Arctic Ocean to the north, and the Norwegian Sea and Iceland to the south. The Greenland Sea is often defined as part of the Arctic Ocean, sometimes as part of the Atlantic Ocean. However, definitions of the Arctic Ocean and its seas tend to be imprecise or arbitrary. In general usage the term "Arctic Ocean" would exclude the Greenland Sea. In oceanographic studies the Greenland Sea is considered part of the Nordic Seas, along with the Norwegian Sea. The Nordic Seas are the main connection between the Arctic and Atlantic oceans and, as such, could be of great significance in a possible shutdown of thermohaline circulation. In oceanography the Arctic Ocean and Nordic Seas are often referred to collectively as the "Arctic Mediterranean Sea", a marginal sea of the Atlantic.The sea has Arctic climate with regular northern winds and temperatures rarely rising above 0 °C (32 °F). It previously contained the Odden ice tongue (or Odden) area, which extended eastward from the main East Greenland ice edge in the vicinity of 72–74°N during the winter and acted as a key winter ice formation area in the Arctic. The West Ice forms in winter in the Greenland Sea, north of Iceland, between Greenland and Jan Mayen island. It is a major breeding ground of harp seal and hooded seal that has been used for seal hunting for more than 200 years.

Indian Ocean Dipole

The Indian Ocean Dipole (IOD), also known as the Indian Niño, is an irregular oscillation of sea-surface temperatures in which the western Indian Ocean becomes alternately warmer and then colder than the eastern part of the ocean.

Monsoon in India is generally affected by the temperature between bay of Bengal in the east and The Arabian sea in the west.

Land use, land-use change, and forestry

Land use, land-use change, and forestry (LULUCF), also referred to as Forestry and other land use (FOLU), is defined by the United Nations Climate Change Secretariat as a "greenhouse gas inventory sector that covers emissions and removals of greenhouse gases resulting from direct human-induced land use such as settlements and commercial uses, land-use change, and forestry activities."LULUCF has impacts on the global carbon cycle and as such, these activities can add or remove carbon dioxide (or, more generally, carbon) from the atmosphere, influencing climate. LULUCF has been the subject of two major reports by the Intergovernmental Panel on Climate Change (IPCC). Additionally, land use is of critical importance for biodiversity.

List of environmental issues

This is an alphabetical list of environmental issues, harmful aspects of human activity on the biophysical environment. They are loosely divided into causes, effects and mitigation, noting that effects are interconnected and can cause new effects.

Outline of environmentalism

The following outline is provided as an overview of and topical guide to environmentalism:

Environmentalism – broad philosophy, ideology and social movement regarding concerns for environmental conservation and improvement of the health of the environment, particularly as the measure for this health seeks to incorporate the concerns of non-human elements. Environmentalism advocates the preservation, restoration and/or improvement of the natural environment, and may be referred to as a movement to control pollution.

Peter Wadhams

Peter Wadhams ScD (born 14 May 1948), is professor of Ocean Physics, and Head of the Polar Ocean Physics Group

in the Department of Applied Mathematics and Theoretical Physics, University of Cambridge. He is best known for his work on sea ice.

Physical impacts of climate change

This article is about the physical impacts of climate change. For some of these physical impacts, their effect on social and economic systems are also described.

This article refers to reports produced by the IPCC. In their usage, "climate change" refers to a change in the state of the climate that can be identified by changes in the mean and/or variability of its properties, and that persists for extended periods, typically decades or longer (IPCC, 2007d:30). The climate change referred to may be due to natural causes and/or the result of human activity.

Rising Tide North America

Rising Tide North America is a grassroots network of groups and individuals in North America organizing action against the root causes of climate change and work towards a non-carbon society. Rising Tide North America is part of an international network dedicated to building a climate justice and anti-extraction movement. Rising Tide generally takes a strongly "no compromise" stance on the environment and a vehement opposition to solutions proposed by corporations who, they say, are responsible for creating environmental problems in the first place.


Shutdown (noun) or shut down (verb) may refer to:

Government shutdown (in the United States)

Occupational burnout

Shutdown (computing)

Shutdown (economics)

Shutdown (nuclear reactor)

Shutdown of thermohaline circulation

Shut down valve

General strike

Thermohaline circulation

Thermohaline circulation (THC) is a part of the large-scale ocean circulation that is driven by global density gradients created by surface heat and freshwater fluxes. The adjective thermohaline derives from thermo- referring to temperature and -haline referring to salt content, factors which together determine the density of sea water. Wind-driven surface currents (such as the Gulf Stream) travel polewards from the equatorial Atlantic Ocean, cooling en route, and eventually sinking at high latitudes (forming North Atlantic Deep Water). This dense water then flows into the ocean basins. While the bulk of it upwells in the Southern Ocean, the oldest waters (with a transit time of around 1000 years) upwell in the North Pacific. Extensive mixing therefore takes place between the ocean basins, reducing differences between them and making the Earth's oceans a global system. On their journey, the water masses transport both energy (in the form of heat) and mass of substances (solids, dissolved substances and gases) around the globe. As such, the state of the circulation has a large impact on the climate of the Earth.

The thermohaline circulation is sometimes called the ocean conveyor belt, the great ocean conveyor, or the global conveyor belt. On occasion, it is used to refer to the meridional overturning circulation (often abbreviated as MOC). The term MOC is more accurate and well defined, as it is difficult to separate the part of the circulation which is driven by temperature and salinity alone as opposed to other factors such as the wind and tidal forces. Moreover, temperature and salinity gradients can also lead to circulation effects that are not included in the MOC itself.

Top contributors to greenhouse gas emissions

This is a collection of the results of various studies regarding the top contributors to atmospheric greenhouse gases responsible for climate change.

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