Query: Modellers assume carbon dioxide drives climate change

Relevant passages:
Attribution of recent climate change <=SEP=> Attribution of recent climate change is the effort to scientifically ascertain mechanisms responsible for recent climate changes on Earth , commonly known as ` global warming ' . The effort has focused on changes observed during the period of instrumental temperature record , when records are most reliable ; particularly in the last 50 years , when human activity has grown fastest and observations of the troposphere have become available . The dominant mechanisms are anthropogenic , i.e. , the result of human activity . They are :  increasing atmospheric concentrations of greenhouse gases  global changes to land surface , such as deforestation  increasing atmospheric concentrations of aerosols .   There are also natural mechanisms for variation including climate oscillations , changes in solar activity , and volcanic activity .   According to the Intergovernmental Panel on Climate Change ( IPCC ) , it is `` extremely likely '' that human influence was the dominant cause of global warming between 1951 and 2010 . The IPCC defines `` extremely likely '' as indicating a probability of 95 to 100 % , based on an expert assessment of all the available evidence .   Multiple lines of evidence support attribution of recent climate change to human activities :  A basic physical understanding of the climate system : greenhouse gas concentrations have increased and their warming properties are well-established .  Historical estimates of past climate changes suggest that the recent changes in global surface temperature are unusual .  Computer-based climate models are unable to replicate the observed warming unless human greenhouse gas emissions are included .  Natural forces alone ( such as solar and volcanic activity ) can not explain the observed warming .   The IPCC 's attribution of recent global warming to human activities is a view shared by the scientific community , and is also supported by 196 other scientific organizations worldwide ( see also : scientific opinion on climate change ) .

Climate change feedback <=SEP=> Climate change feedback is important in the understanding of global warming because feedback processes may amplify or diminish the effect of each climate forcing , and so play an important part in determining the climate sensitivity and future climate state . Feedback in general is the process in which changing one quantity changes a second quantity , and the change in the second quantity in turn changes the first . Positive feedback amplifies the change in the first quantity while negative feedback reduces it .   The term `` forcing '' means a change which may `` push '' the climate system in the direction of warming or cooling . An example of a climate forcing is increased atmospheric concentrations of greenhouse gases . By definition , forcings are external to the climate system while feedbacks are internal ; in essence , feedbacks represent the internal processes of the system . Some feedbacks may act in relative isolation to the rest of the climate system ; others may be tightly coupled ; hence it may be difficult to tell just how much a particular process contributes . Forcings , feedbacks and the dynamics of the climate system determine how much and how fast the climate changes . The main positive feedback in global warming is the tendency of warming to increase the amount of water vapor in the atmosphere , which in turn leads to further warming . The main negative feedback comes from the Stefan -- Boltzmann law , the amount of heat radiated from the Earth into space changes with the fourth power of the temperature of Earth 's surface and atmosphere .   Some observed and potential effects of global warming are positive feedbacks , which contribute directly to further global warming . The Intergovernmental Panel on Climate Change 's ( IPCC ) Fourth Assessment Report states that `` Anthropogenic warming could lead to some effects that are abrupt or irreversible , depending upon the rate and magnitude of the climate change . ''

Climate change (general concept) <=SEP=> Climate variability includes all the variations in the climate that last longer than individual weather events, whereas the term climate change only refers to those variations that persist for a longer period of time, typically decades or more. In the time since the industrial revolution the climate has increasingly been affected by human activities that are causing global warming and climate change.The climate system receives nearly all of its energy from the sun. The climate system also radiates energy to outer space. The balance of incoming and outgoing energy, and the passage of the energy through the climate system, determines Earth\'s energy budget. When the incoming energy is greater than the outgoing energy, earth\'s energy budget is positive and the climate system is warming. If more energy goes out, the energy budget is negative and earth experiences cooling.\nThe energy moving through Earth\'s climate system finds expression in weather, varying on geographic scales and time. Long-term averages and variability of weather in a region constitute the region\'s climate. Such changes can be the result of "internal variability", when natural processes inherent to the various parts of the climate system alter the distribution of energy. Examples include variability in ocean basins such as the Pacific decadal oscillation and Atlantic multidecadal oscillation. Climate variability can also result from external forcing, when events outside of the climate system\'s components nonetheless produce changes within the system. Examples include changes in solar output and volcanism.\nClimate variability has consequences for sea level changes, plant life, and mass extinctions; it also affects human societies.

Carbon dioxide in Earth's atmosphere <=SEP=> Carbon dioxide is an important trace gas in Earth 's atmosphere . Currently it constitutes about 0.041 % ( equal to 410 parts per million ; ppm ) by volume of the atmosphere . Despite its relatively small concentration is a potent greenhouse gas and plays a vital role in regulating Earth 's surface temperature through radiative forcing and the greenhouse effect . Reconstructions show that concentrations of in the atmosphere have varied , ranging from as high as 7,000 ppm during the Cambrian period about 500 million years ago to as low as 180 ppm during the Quaternary glaciation of the last two million years .   Carbon dioxide is an integral part of the carbon cycle , a biogeochemical cycle in which carbon is exchanged between the Earth 's oceans , soil , rocks and the biosphere . Plants and other photoautotrophs use solar energy to produce carbohydrate from atmospheric carbon dioxide and water by photosynthesis . Almost all other organisms depend on carbohydrate derived from photosynthesis as their primary source of energy and carbon compounds .   The current episode of global warming is attributed to increasing emissions of and other greenhouse gases into Earth 's atmosphere . The global annual mean concentration of in the atmosphere has increased by more than 40 % since the start of the Industrial Revolution , from 280 ppm , the level it had for the last 10,000 years leading up to the mid-18th century , to 399 ppm as of 2015 . The present concentration is the highest in at least the past 800,000 years and likely the highest in the past 20 million years . The increase has been caused by anthropogenic sources , particularly the burning of fossil fuels and deforestation . The daily average concentration of atmospheric CO2 at Mauna Loa Observatory first exceeded 400 ppm on 10 May 2013 . It is currently rising at a rate of approximately 2 ppm/year and accelerating . An estimated 30 -- 40 % of the released by humans into the atmosphere dissolves into oceans , rivers and lakes , which contributes to ocean acidification .