In Terms Of Atmospheric Change, Which Of The Following Is True?

On This Page:

• Earth's temperature is a balancing deed
• The greenhouse effect causes the temper to retain heat
• Changes in the sun's energy affect how much energy reaches Earth's organisation
• Changes in reflectivity impact how much energy enters Earth's system

---

Globe's temperature is a balancing human action

Models that account merely 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 by humans are able to explicate this warming.

Click the image to view a larger version.

Earth'southward temperature depends on the balance between energy inbound and leaving the planet'due south organisation. When incoming free energy from the lord's day is absorbed by the Earth system, Earth warms. When the dominicus's free energy is reflected back into infinite, Earth avoids warming. When absorbed energy is released back into infinite, World cools. Many factors, both natural and homo, tin cause changes in Earth'due south energy balance, including:

• Variations in the sunday's energy reaching Globe
• Changes in the reflectivity of Globe'south temper and surface
• Changes in the greenhouse effect, which affects the amount of heat retained by Earth's temper

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

Scientists have pieced together a record of Earth's climate, dating back 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 as water ice cores, tree rings, glacier lengths, pollen remains, and bounding main sediments, and by studying changes in World'south orbit around the sun.^[2]

This tape 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 equally changes in solar energy, volcanic eruptions, and natural changes in greenhouse gas (GHG) concentrations.^[ii]

Recent climate changes, withal, cannot be explained by natural causes alone. Inquiry indicates that natural causes do not explain well-nigh observed warming, peculiarly warming since the mid-20^th century. Rather, it is extremely probable that homo activities have been the dominant cause of that warming.^[2]

Pinnacle of Folio

The greenhouse effect causes the atmosphere to retain heat

When sunlight reaches Earth's surface, information technology can either be reflected back into space or absorbed by Earth. Once absorbed, the planet releases some of the energy back into the atmosphere as estrus (likewise called infrared radiations). Greenhouse gases like water vapor (H₂O), carbon dioxide (CO₂), and methane (CH₄) absorb energy, slowing or preventing the loss of rut to space. In this way, GHGs deed like a coating, making Globe warmer than it would otherwise be. This process is normally known every bit the "greenhouse upshot."

The role of the greenhouse effect in the past

Over the last several hundred thousand years, CO₂ levels varied in tandem with the glacial cycles. During warm "interglacial" periods, CO_two levels were higher. During absurd "glacial" periods, CO₂ levels were lower.^[2] The heating or cooling of Earth'south surface and oceans can cause changes in the natural sources and sinks of these gases, and thus change greenhouse gas concentrations in the atmosphere.^[2] These changing concentrations are thought to have acted every bit a positive feedback, amplifying the temperature changes caused by long-term shifts in Earth'southward orbit.^[2]

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

Click the epitome to view a larger version.
Source: Based on data actualization in NRC (2010).

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

Click the image to view a larger version.
Source: U.S. National Climate Assessment (2014).

The recent role of the greenhouse effect

Since the Industrial Revolution began effectually 1750, human activities accept contributed essentially to climatic change past calculation CO_ii and other estrus-trapping gases to the temper. These greenhouse gas emissions accept increased the greenhouse event and caused Earth's surface temperature to rise. The primary human activity affecting the amount and rate of climate alter is greenhouse gas emissions from the called-for of fossil fuels.

The main greenhouse gases

The most important GHGs directly emitted by humans include carbon dioxide (CO_ii), methane (CH₄), nitrous oxide (N₂O), and several others. The sources and recent trends of these gases are detailed below.

Carbon dioxide

Carbon dioxide is the primary greenhouse gas that is contributing to recent climate change. CO₂ is absorbed and emitted naturally as part of the carbon cycle, through found and animal respiration, volcanic eruptions, and ocean-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 CO₂ concentrations have increased by more than 40% 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 fourth dimension in human history. The electric current CO₂ level is college than it has been in at to the lowest degree 800,000 years.^[2]

Some volcanic eruptions released large quantities of CO₂ in the distant past. However, the U.S. Geological Survey (USGS) reports that human activities at present emit more than than 135 times as much CO_two 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 temper is like a tub filling with water, where more than water flows from the faucet than the bleed can have away.

Atmospheric carbon dioxide concentration has risen from pre-industrial levels of 280 parts per 1000000 past volume (ppmv) to over 401 ppmv in 2016. Since 1959 alone (shown here), concentrations have risen by more than than 85 ppmv. The yearly ascent and fall in the nautical chart reflects the growth and disuse or northern hemisphere vegetation.

Click the epitome to view a larger version.
Source: NOAA

If the amount of water flowing into a bathrub is greater than the amount of h2o leaving through the drain, the h2o level will rise. CO_two emissions are like the catamenia of water into the world's carbon bathtub. "Sources" of CO₂ emissions such equally fossil fuel burning, cement manufacture, and land use are like the bathtub'due south faucet. "Sinks" of CO₂ in the body of water and on state (such as plants) that take upwardly CO_two are like the drain. Today, human activities have turned up the flow from the CO₂ "faucet," which is much larger than the "drain" can cope with, and the level of CO_two 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 can reduce emissions, see the Carbon Dioxide page in the Greenhouse Gas Emissions website.

Methyl hydride

Methane is produced through both natural and human activities. For instance, natural wetlands, agricultural activities, and fossil fuel extraction and transport all emit CH₄.

Methane is more abundant in Earth's temper now than at any time in at least the by 800,000 years.^[2] Due to human activities, CH_ivconcentrations increased sharply during nearly of the 20th century and are now more than than ii-and-a-half times pre-industrial levels. In recent decades, the rate of increase has slowed considerably.^[two]

For more information on CH₄ emissions and sources, and actions that can reduce emissions, encounter EPA's Marsh gas page in the Greenhouse Gas Emissions website. For information on how marsh gas is impacting the Arctic, come across the EPA reportMethane and Black Carbon Impacts on the Arctic.

Nitrous oxide

Nitrous oxide is produced through natural and human activities, mainly through agricultural activities and natural biological processes. Fuel burning and some other processes also create N_iiO. Concentrations of Northward₂O take risen approximately 20% since the starting time of the Industrial Revolution, with a relatively rapid increase toward the end of the 20th century.^[2]

Overall, N₂O concentrations have increased more rapidly during the past century than at any time in the by 22,000 years.^[2] For more information on N_iiO emissions and sources, and deportment that can reduce emissions, see EPA'southward Nitrous Oxide page in the Greenhouse Gas Emissions website.

Other greenhouse gases

• Water vapor is the most arable greenhouse gas and as well the virtually important in terms of its contribution to the natural greenhouse outcome, despite having a short atmospheric lifetime. Some human activities tin influence local water vapor levels. However, on a global scale, the concentration of water vapor is controlled by temperature, which influences overall rates of evaporation and atmospheric precipitation.^[two] Therefore, the global concentration of water vapor is non essentially affected by direct human emissions.
• Tropospheric ozone (O_three), which also has a short atmospheric lifetime, is a potent greenhouse gas. Chemic reactions create ozone from emissions of nitrogen oxides and volatile organic compounds from automobiles, power plants, and other industrial and commercial sources in the presence of sunlight. In improver to trapping heat, footing-level ozone is a pollutant that can crusade 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, fire extinguishers, solvents, pesticides, and aerosol propellants. Unlike h2o vapor and ozone, these F-gases have a long atmospheric lifetime, and some of these emissions will 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 mensurate the relative strengths of greenhouse gases. To acquire more nearly actions that can reduce these emissions, see What You Can Do.

Other climate forcers

Particles and aerosols in the atmosphere tin can as well affect climate. Human activities such equally burning fossil fuels and biomass contribute to emissions of these substances, although some aerosols also come up 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. Dissimilar GHGs, BC can directly absorb incoming and reflected sunlight in improver to arresting infrared radiation. BC tin can also exist deposited on snowfall and ice, darkening the surface and thereby increasing the snow's absorption of sunlight and accelerating cook. For information on how BC is impacting the Arctic, come across EPA assessmentMethane and Black Carbon Impacts on the Arctic.
• Sulfates, organic carbon, and other aerosols tin crusade cooling by reflecting sunlight.
• Warming and cooling aerosols can collaborate with clouds, changing a number of cloud attributes such as their formation, dissipation, reflectivity, and atmospheric precipitation rates. Clouds can contribute both to cooling, by reflecting sunlight, and warming, past trapping outgoing heat.

For more information on greenhouse gas emissions, run into the Greenhouse Gas Emissions website. To learn more well-nigh actions that can reduce these emissions, meet What EPA is Doing and What You Tin can Do.

Top of Page

Changes in the dominicus's energy affect how much energy reaches Globe'due south arrangement

The sun's energy received at the top of World'southward atmosphere has been measured past satellites since 1978. It has followed its natural 11-yr wheel of small ups and downs, merely with no internet increase (bottom). Over the same catamenia, global temperature has risen markedly (top).

Click the image to view a larger version.
Source: USGCRP (2009).

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

Changes occurring in the sun itself can impact the intensity of the sunlight that reaches Earth's 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 dominicus follows a natural eleven-year wheel of small ups and downs in intensity, but the effect on Earth's climate is small.^[i]

Changes in the shape of World's orbit as well as the tilt and position of Earth's axis can also affect the amount of sunlight reaching Globe's surface.^{[1] [2]}

The role of the sun's energy in the by

Changes in the sun's intensity have influenced World'southward climate in the past. For example, the so-chosen "Little Water ice Age" betwixt the 17th and 19th centuries may have 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 Earth'south orbit have had a big impact on climate over tens to hundreds of thousands of years. In fact, the amount of summer sunshine on the Northern Hemisphere, which is afflicted by changes in the planet'south orbit, appears to drive 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 cold temperatures (water ice ages), as well every bit shorter interglacial periods (periods between ice ages) of relatively warmer temperatures.^{[1] [2]}

Rates of Climate change Have Varied Over Time

Click to learn most how rates of climate modify have varied over time.

The recent role of the lord's day's energy

Changes in solar energy continue to bear on climate. Yet, over the last 11-twelvemonth solar bicycle, solar output has been lower than it has been since the mid-20^th century, and therefore does not explicate the recent warming of the world.^[2] Similarly, changes in the shape of Earth's orbit as well as the tilt and position of Globe's axis touch temperature on very long timescales (tens to hundreds of thousands of years), and therefore cannot explain the recent warming.

Changes in reflectivity touch on how much energy enters Earth's organisation

When sunlight reaches Earth, it can be reflected or captivated. The amount that is reflected or absorbed depends on Globe'southward surface and atmosphere. Light-colored objects and surfaces, like snowfall and clouds, tend to reflect most sunlight, while darker objects and surfaces, like the body of water, forests, or soil, tend to absorb more sunlight.

The term albedo refers to the amount of solar radiations reflected from an object or surface, often expressed as a percent. Globe every bit a whole has an albedo of about 30%, meaning that 70% of the sunlight that reaches the planet is captivated.^[3] Absorbed sunlight warms Earth's land, h2o, and atmosphere.

Reflectivity is too affected by aerosols. Aerosols are modest particles or liquid droplets in the temper that can absorb or reverberate 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 as particles from volcanic eruptions or sulfur emissions from burning coal, have a cooling effect. Those that absorb sunlight, such equally black carbon (a part of soot), take a warming event.

The role of reflectivity in the past

Natural changes in reflectivity, like the melting of sea ice, have contributed to climate change in the past, often interim as feedbacks to other processes.

Volcanoes have played a noticeable role in climate. Volcanic particles that reach the upper atmosphere tin reverberate enough sunlight back to space to absurd the surface of the planet by a few tenths of a degree for several years.^[2] These particles are an example of cooling aerosols. Volcanic particles from a single eruption do non produce long-term change because they remain in the atmosphere for a much shorter time than GHGs.^[2]

The recent part of reflectivity

Human changes in land use and land encompass have changed Globe'due south reflectivity. Processes such equally deforestation, reforestation, desertification, and urbanization often contribute to changes in climate in the places they occur. These effects may be significant regionally, but are smaller when averaged over the entire globe.

In addition, human activities accept generally increased the number of aerosol particles in the atmosphere. Overall, human-generated aerosols take a net cooling effect offsetting near ane-third of the full warming effect associated with human greenhouse gas emissions. Reductions in overall aerosol emissions tin can therefore pb to more warming. However, targeted reductions in black carbon emissions can reduce warming.^[1]

Top of Page

---

References:

[1] USGCRP (2014). Climate change Impacts in the U.s.: The Third National Climate Assessment. [Melillo, Jerry Grand., Terese (T.C.) Richmond, and Gary W. Yohe, Eds.] U.S. Global Change Inquiry Program.

[2] IPCC (2013).Climate Modify 2013: The Physical Science Basis.Contribution of Working Group I to the Fifth Cess Written report of the Intergovernmental Panel on Climatic change [Stocker, T.F., D. Qin, G.-K. Plattner, Chiliad. 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, Us.

[iii] NRC (2010).Advancing the Scientific discipline of Climate Changes . National Inquiry Council. The National Academies Printing, Washington, DC, United states.

Acme of Page

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

Posted by: cookrowasoul1987.blogspot.com

Share this post