what factor in the atmosphere seems to have the greatest effect on radiation coming from the sun

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• Globe's temperature is a balancing act
• The greenhouse effect causes the temper to retain rut
• Changes in the dominicus'due south energy bear upon how much energy reaches Earth's system
• Changes in reflectivity affect how much energy enters Earth'due south organization

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Earth's temperature is a balancing deed

Models that account only for the effects of natural processes are not able to explain the warming observed over the past century. Models that also account for the greenhouse gases emitted past humans are able to explain this warming.

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World's temperature depends on the residue between free energy entering and leaving the planet's system. When incoming energy from the sun is absorbed by the Earth system, World warms. When the sun's energy is reflected back into infinite, Globe avoids warming. When absorbed free energy is released back into space, Earth cools. Many factors, both natural and human, can cause changes in Earth's energy rest, including:

• Variations in the sun's free energy reaching Earth
• Changes in the reflectivity of Globe's temper and surface
• Changes in the greenhouse result, which affects the amount of oestrus retained by Earth's atmosphere

These factors have acquired Earth's climate to modify many times.

Scientists have pieced together a record of Earth'due south climate, dating dorsum hundreds of thousands of years (and, in some cases, millions or hundreds of millions of years), by analyzing a number of indirect measures of climate such every bit ice cores, tree rings, glacier lengths, pollen remains, and ocean sediments, and past studying changes in Earth's orbit around the sun.^[2]

This record shows that the climate system varies naturally over a wide range of time scales. In general, climate changes prior to the Industrial Revolution in the 1700s can be explained by natural causes, such as changes in solar energy, volcanic eruptions, and natural changes in greenhouse gas (GHG) concentrations.^[ii]

Recent climate changes, however, cannot be explained by natural causes solitary. Research indicates that natural causes exercise non explain about observed warming, especially warming since the mid-20^th century. Rather, it is extremely likely that homo activities have been the dominant cause of that warming.^[2]

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The greenhouse effect causes the atmosphere to retain heat

When sunlight reaches Globe'southward surface, information technology can either be reflected back into infinite or captivated past Globe. Once captivated, the planet releases some of the energy back into the atmosphere equally heat (likewise chosen infrared radiation). Greenhouse gases similar water vapor (H_iiO), carbon dioxide (CO₂), and methane (CH₄) absorb energy, slowing or preventing the loss of heat to space. In this way, GHGs act like a blanket, making Globe warmer than it would otherwise exist. This procedure is ordinarily known as the "greenhouse effect."

The office of the greenhouse effect in the past

Over the last several hundred one thousand years, CO_two levels varied in tandem with the glacial cycles. During warm "interglacial" periods, CO₂ levels were higher. During cool "glacial" periods, CO_ii levels were lower.^[2] The heating or cooling of Earth's surface and oceans tin can cause changes in the natural sources and sinks of these gases, and thus modify greenhouse gas concentrations in the atmosphere.^[ii] These irresolute concentrations are thought to have acted as a positive feedback, amplifying the temperature changes caused past long-term shifts in World'southward orbit.^[2]

Estimates of the Earth's irresolute CO_ii concentration (pinnacle) and Antarctic temperature (bottom), based on analysis of ice core data extending back 800,000 years. Until the past century, natural factors acquired atmospheric CO₂ concentrations to vary within a range of about 180 to 300 parts per 1000000 by book (ppmv). Warmer periods coincide with periods of relatively high CO_two concentrations. Note: The past century'southward temperature changes and rapid CO_two rise (to 400 ppmv in 2015) are not shown here. Increases over the past half century are shown in the Recent Role section.

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Source: Based on data actualization in NRC (2010).

This graph shows the increase in greenhouse gas (GHG) concentrations in the atmosphere over the concluding 2,000 years. Increases in concentrations of these gases since 1750 are due to homo activities in the industrial era. Concentration units are parts per 1000000 (ppm) or parts per billion (ppb), indicating the number of molecules of the greenhouse gas per one thousand thousand or billion molecules of air.

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Source: U.South. National Climate Assessment (2014).

The recent role of the greenhouse effect

Since the Industrial Revolution began around 1750, human activities have contributed essentially to climate change by adding CO₂ and other heat-trapping gases to the atmosphere. These greenhouse gas emissions have increased the greenhouse effect and acquired Globe's surface temperature to rise. The master man activity affecting the amount and rate of climatic change is greenhouse gas emissions from the burning of fossil fuels.

The master greenhouse gases

The virtually important GHGs directly emitted past humans include carbon dioxide (CO₂), methyl hydride (CH₄), nitrous oxide (N₂O), and several others. The sources and recent trends of these gases are detailed beneath.

Carbon dioxide

Carbon dioxide is the chief greenhouse gas that is contributing to contempo climate alter. CO₂ is absorbed and emitted naturally equally role of the carbon cycle, through plant and animal respiration, volcanic eruptions, and body of water-atmosphere exchange. Human activities, such every bit the burning of fossil fuels and changes in land use, release large amounts of CO₂, causing concentrations in the atmosphere to rise.

Atmospheric CO_ii concentrations have increased by more than xl% since pre-industrial times, from approximately 280 parts per million by volume (ppmv) in the 18th century to over 400 ppmv in 2015. The monthly boilerplate concentration at Mauna Loa now exceeds 400 ppmv for the first time in human history. The current CO₂ level is higher than information technology has been in at least 800,000 years.^[ii]

Some volcanic eruptions released large quantities of CO₂ in the distant past. Even so, the U.S. Geological Survey (USGS) reports that human activities now emit more 135 times equally much CO₂ as volcanoes each yr.

Human activities currently release over 30 billion tons of CO₂ into the temper every year.^[ii] The resultant build-up of CO₂ in the atmosphere is similar a tub filling with water, where more water flows from the faucet than the drain can take abroad.

Atmospheric carbon dioxide concentration has risen from pre-industrial levels of 280 parts per million by volume (ppmv) to over 401 ppmv in 2016. Since 1959 lonely (shown here), concentrations have risen by more than than 85 ppmv. The yearly rising and fall in the chart reflects the growth and decay or northern hemisphere vegetation.

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Source: NOAA

If the amount of h2o flowing into a bathrub is greater than the corporeality of h2o leaving through the drain, the water level volition rise. CO₂ emissions are like the menstruation of h2o into the world's carbon bathtub. "Sources" of CO_ii emissions such every bit fossil fuel burning, cement manufacture, and country utilize are like the bathtub's faucet. "Sinks" of CO₂ in the body of water and on land (such every bit plants) that accept upwardly CO₂ are like the drain. Today, human activities have turned upward the catamenia from the CO₂ "faucet," which is much larger than the "drain" can cope with, and the level of CO_ii in the atmosphere (like the level of water in a bathtub) is rising.

For more information on the human and natural sources and sinks of CO₂ emissions, and actions that tin reduce emissions, meet the Carbon Dioxide page in the Greenhouse Gas Emissions website.

Methane

Methane is produced through both natural and homo activities. For example, natural wetlands, agricultural activities, and fossil fuel extraction and transport all emit CH_four.

Methane is more abundant in World's atmosphere now than at any time in at least the by 800,000 years.^[2] Due to homo activities, CH_ivconcentrations increased sharply during almost of the 20th century and are at present more than two-and-a-one-half times pre-industrial levels. In recent decades, the charge per unit of increase has slowed considerably.^[2]

For more data on CH₄ emissions and sources, and deportment that tin reduce emissions, see EPA's Methane folio in the Greenhouse Gas Emissions website. For information on how methane is impacting the Chill, see the EPA reportMethane and Black Carbon Impacts on the Arctic.

Nitrous oxide

Nitrous oxide is produced through natural and homo activities, mainly through agronomical activities and natural biological processes. Fuel called-for and some other processes also create N₂O. Concentrations of N₂O accept risen approximately 20% since the start of the Industrial Revolution, with a relatively rapid increase toward the terminate of the 20th century.^[2]

Overall, N₂O concentrations have increased more rapidly during the by century than at whatsoever fourth dimension in the past 22,000 years.^[2] For more data on Due north₂O emissions and sources, and actions that tin can reduce emissions, see EPA's Nitrous Oxide page in the Greenhouse Gas Emissions website.

Other greenhouse gases

• Water vapor is the most abundant greenhouse gas and as well the almost important in terms of its contribution to the natural greenhouse effect, despite having a short atmospheric lifetime. Some man activities can influence local water vapor levels. Nevertheless, on a global scale, the concentration of water vapor is controlled past temperature, which influences overall rates of evaporation and precipitation.^[two] Therefore, the global concentration of water vapor is not substantially affected past straight human emissions.
• Tropospheric ozone (O₃), which as well has a curt atmospheric lifetime, is a stiff greenhouse gas. Chemical reactions create ozone from emissions of nitrogen oxides and volatile organic compounds from automobiles, ability plants, and other industrial and commercial sources in the presence of sunlight. In addition to trapping heat, ground-level ozone is a pollutant that can cause respiratory health problems and damage crops and ecosystems.
• Chlorofluorocarbons (CFCs), hydrochlorofluorocarbons (HCFCs), hydrofluorocarbons (HFCs), perfluorocarbons (PFCs), and sulfur hexafluoride (SF₆), together called F-gases, are often used in coolants, foaming agents, burn down extinguishers, solvents, pesticides, and aerosol propellants. Unlike h2o vapor and ozone, these F-gases have a long atmospheric lifetime, and some of these emissions volition affect the climate for many decades or centuries.

For more information on greenhouse gas emissions, see the Greenhouse Gas Emissions website, including an expanded discussion of global warming potentials and how they are used to measure the relative strengths of greenhouse gases. To learn more about actions that can reduce these emissions, run across What You Can Do.

Other climate forcers

Particles and aerosols in the temper tin also affect climate. Human activities such as burning fossil fuels and biomass contribute to emissions of these substances, although some aerosols as well come from natural sources such as volcanoes and marine plankton.

• Black carbon (BC) is a solid particle or aerosol, not a gas, but it also contributes to warming of the atmosphere. Unlike GHGs, BC tin can directly absorb incoming and reflected sunlight in improver to absorbing infrared radiations. BC can besides exist deposited on snow and water ice, darkening the surface and thereby increasing the snow's absorption of sunlight and accelerating melt. For information on how BC is impacting the Arctic, see EPA cessMethane and Black Carbon Impacts on the Arctic.
• Sulfates, organic carbon, and other aerosols can cause cooling by reflecting sunlight.
• Warming and cooling aerosols can interact with clouds, changing a number of cloud attributes such equally their formation, dissipation, reflectivity, and precipitation rates. Clouds can contribute both to cooling, by reflecting sunlight, and warming, by trapping approachable rut.

For more than information on greenhouse gas emissions, run across the Greenhouse Gas Emissions website. To learn more near actions that can reduce these emissions, meet What EPA is Doing and What You Can Do.

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Changes in the sun'south energy touch on how much energy reaches Globe'due south organisation

The sun's energy received at the acme of Earth'southward temper has been measured by satellites since 1978. It has followed its natural 11-year cycle of modest ups and downs, but with no net increase (lesser). Over the aforementioned period, global temperature has risen markedly (top).

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Source: USGCRP (2009).

Climate is influenced past natural changes that affect how much solar energy reaches World. These changes include changes within the sun and changes in Earth's orbit.

Changes occurring in the sun itself can touch on the intensity of the sunlight that reaches Earth'due south surface. The intensity of the sunlight can cause either warming (during periods of stronger solar intensity) or cooling (during periods of weaker solar intensity). The sun follows a natural 11-year cycle of minor ups and downs in intensity, but the issue on Earth'south climate is small-scale.^[1]

Changes in the shape of Globe'due south orbit also every bit the tilt and position of Globe's centrality tin can also affect the amount of sunlight reaching Earth'due south surface.^{[1] [2]}

The part of the sun's energy in the past

Changes in the sun's intensity have influenced Globe's climate in the past. For example, the so-called "Picayune Ice Age" between the 17th and 19th centuries may take been partially caused by a low solar activeness stage from 1645 to 1715, which coincided with cooler temperatures. The "Little Ice Age" refers to a slight cooling of North America, Europe, and probably other areas around the globe.^[2]

Changes in Globe's orbit take had a big affect on climate over tens to hundreds of thousands of years. In fact, the amount of summer sunshine on the Northern Hemisphere, which is afflicted past changes in the planet's orbit, appears to bulldoze the advance and retreat of ice sheets. These changes appear to be the primary cause of past cycles of ice ages, in which Earth has experienced long periods of common cold temperatures (ice ages), too equally shorter interglacial periods (periods between ice ages) of relatively warmer temperatures.^{[1] [2]}

Rates of Climate change Have Varied Over Time

Click to learn about how rates of climate change have varied over time.

The recent role of the sun's free energy

Changes in solar free energy continue to affect climate. However, over the last 11-year solar cycle, solar output has been lower than it has been since the mid-twenty^th century, and therefore does not explain the contempo warming of the earth.^[two] Similarly, changes in the shape of Earth's orbit too as the tilt and position of Earth'southward axis affect temperature on very long timescales (tens to hundreds of thousands of years), and therefore cannot explain the contempo warming.

Changes in reflectivity affect how much energy enters Earth's organisation

When sunlight reaches Earth, it tin exist reflected or captivated. The amount that is reflected or captivated depends on Globe's surface and atmosphere. Light-colored objects and surfaces, like snow and clouds, tend to reflect nearly sunlight, while darker objects and surfaces, similar the ocean, forests, or soil, tend to absorb more sunlight.

The term albedo refers to the amount of solar radiation reflected from an object or surface, often expressed as a per centum. Earth as a whole has an albedo of about 30%, meaning that 70% of the sunlight that reaches the planet is absorbed.^[3] Captivated sunlight warms Earth's land, water, and atmosphere.

Reflectivity is too affected by aerosols. Aerosols are pocket-size particles or liquid aerosol in the atmosphere that tin can absorb or reflect sunlight. Unlike greenhouse gases, the climate effects of aerosols vary depending on what they are made of and where they are emitted. Those aerosols that reflect sunlight, such every bit particles from volcanic eruptions or sulfur emissions from called-for coal, have a cooling effect. Those that absorb sunlight, such as blackness carbon (a part of soot), have a warming effect.

The role of reflectivity in the by

Natural changes in reflectivity, like the melting of ocean ice, have contributed to climate change in the past, ofttimes acting every bit feedbacks to other processes.

Volcanoes accept played a noticeable office in climate. Volcanic particles that achieve the upper atmosphere can reflect enough sunlight back to space to cool the surface of the planet by a few tenths of a degree for several years.^[two] These particles are an instance of cooling aerosols. Volcanic particles from a single eruption do not produce long-term change considering they remain in the atmosphere for a much shorter time than GHGs.^[2]

The recent role of reflectivity

Human changes in land use and land cover accept changed Earth's reflectivity. Processes such equally deforestation, reforestation, desertification, and urbanization often contribute to changes in climate in the places they occur. These effects may be pregnant regionally, but are smaller when averaged over the entire world.

In addition, human activities have more often than not increased the number of aerosol particles in the atmosphere. Overall, human-generated aerosols take a net cooling event offsetting virtually i-third of the total warming issue associated with man greenhouse gas emissions. Reductions in overall aerosol emissions can therefore lead to more warming. However, targeted reductions in black carbon emissions tin reduce warming.^[1]

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References:

[i] USGCRP (2014). Climatic change Impacts in the United States: The 3rd National Climate Assessment. [Melillo, Jerry M., Terese (T.C.) Richmond, and Gary W. Yohe, Eds.] U.S. Global Change Research Plan.

[2] IPCC (2013).Climate Change 2013: The Concrete Scientific discipline Basis.Contribution of Working Grouping I to the Fifth Cess Report of the Intergovernmental Console on Climate change [Stocker, T.F., D. Qin, Chiliad.-Thou. Plattner, M. Tignor, S.Yard. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United kingdom and New York, NY, USA.

[iii] NRC (2010).Advancing the Science of Climate Changes . National Inquiry Quango. The National Academies Press, Washington, DC, USA.

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Source: https://19january2017snapshot.epa.gov/climate-change-science/causes-climate-change_.html

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