Climate change is a change in the statistical distribution of weather patterns when that change lasts for an extended period of time (i.e., decades to millions of years). Climate change may refer to a change in average weather conditions, or in the time variation of weather around longer-term average conditions (i.e., more or fewer extreme weather events). Climate change is caused by factors such as biotic processes, variations in solar radiation received by Earth, plate tectonics, and volcanic eruptions. Certain human activities have also been identified as significant causes of recent climate change, often referred to as "global warming".

Scientists actively work to understand past and future climate by using observations and theoretical models. A climate record — extending deep into the Earth's past — has been assembled, and continues to be built up, based on geological evidence from borehole temperature profiles, cores removed from deep accumulations of ice, floral and faunal records, glacial and periglacial processes, stable-isotope and other analyses of sediment layers, and records of past sea levels. More recent data are provided by the instrumental record. General circulation models, based on the physical sciences, are often used in theoretical approaches to match past climate data, make future projections, and link causes and effects in climate change.

The circulation of the Atlantic Ocean plays a key role in regulating global climate. The constantly moving system of deep-water circulation, sometimes referred to as the Global Ocean Conveyor Belt, sends warm, salty Gulf Stream water to the North Atlantic where it releases heat to the atmosphere and warms Western Europe. The cooler water then sinks to great depths and travels all the way to Antarctica and eventually circulates back up to the Gulf Stream (Intergovernmental Panel on Climate Change)

(INDEPENDENT) Disruption of ocean circulation is thought to be driven by global warming, and could lead to sea level rise and extreme events like storms. Catastrophic changes in global weather patterns could be on the horizon as scientists confirm the warming Atlantic current has reached a “new record low”. The Gulf Stream current, which has not been running at peak strength for centuries, is now at its weakest point in the past 1,600 years. Climate change resulting from rising levels of carbon dioxide in the atmosphere is a likely cause of this phenomenon. The Atlantic meridional overturning circulation (Amoc), the system of currents that transports warm water from the tropics via the Gulf Stream to the North Atlantic, plays a major role in regulating the world’s climate.

Climate change mitigation consists of actions to limit the magnitude and/or rate of long-term climate change. Climate change mitigation generally involves reductions in human (anthropogenic) emissions of greenhouse gases. Mitigation may also be achieved by increasing the capacity of carbon sinks, e.g., through reforestation. Mitigation policies can substantially reduce the risks associated with human-induced global warming. Effective climate change mitigation will not be achieved if each agent (individual, institution or country) acts independently in its own selfish interest, suggesting the need for collective action. Some adaptation actions, on the other hand, have characteristics of a private good as benefits of actions may accrue more directly to the individuals, regions, or countries that undertake them, at least in the short term. Nevertheless, financing such adaptive activities remains an issue, particularly for poor individuals and countries.

Climate change denial, or global warming denial, is part of the global warming controversy. It involves denial, dismissal, unwarranted doubt or contrarian views which strongly depart from the scientific opinion on climate change, including the extent to which it is caused by humans, its impacts on nature and human society, or the potential of adaptation to global warming by human actions. Some deniers do endorse the term, but others often prefer the term climate change skepticism. In effect, the two terms form a continuous, overlapping range of views, and generally have the same characteristics; both reject, to a greater or lesser extent, mainstream scientific opinion on climate change. Climate change denial can also be implicit, when individuals or social groups accept the science but fail to come to terms with it or to translate their acceptance into action. Several social science studies have analyzed these positions as forms of denialism. Although scientific opinion on climate change is that human activity is extremely likely to be the primary driver of climate change, the politics of global warming (especially in the US) have been affected by climate change denial, hindering efforts to prevent climate change and adapt to the warming climate. Those promoting denial commonly use rhetorical tactics to give the appearance of a scientific controversy where there is none.

Global Warming Effects and Causes: A Top 10 List

1. Global Warming Cause: Carbon dioxide emissions from fossil fuel burning power plants

2. Global Warming Cause: Carbon dioxide emissions from burning gasoline for transportation

3. Global Warming Cause: Methane emissions from animals, agriculture such as rice paddies, and from Arctic seabeds

4. Global Warming Cause: Deforestation, especially tropical forests for wood, pulp, and farmland

5. Global Warming Cause: Increase in usage of chemical fertilizers on croplands

6. Global Warming Effect: Rise in sea levels worldwide

7. Global Warming Effect: More killer storms

8. Global Warming Effect: Massive crop failures

9. Global Warming Effect: Widespread extinction of species

10. Global Warming Effect: Disappearance of coral reefs