Factors Behind Climate Change

It is much easier to document the evidence of climate variability and past climate change than it really is to determine their underlying mechanisms. Climate is influenced by a multitude of elements that work at timescales ranging from hours to vast sums of years. Many of the factors behind climate change are exterior to the Earth system. Others are part of the Earth system but exterior towards the atmosphere. However others involve interactions involving the atmosphere and other components of the Earth system as they are collectively described as feedbacks within the Earth system. Feedbacks are being among the most recently discovered and challenging causal factors to study. Nevertheless, these elements are increasingly seen as playing fundamental roles in climate variation. The most important mechanisms are described in this section.

Solar variability

The luminosity, or brightness, of the Sun was increasing steadily since its formation. This phenomenon is important to Earth’s climate, because the Sun supplies the energy to drive atmospheric blood flow and constitutes the input for Earth’s heat budget. Low solar luminosity during Precambrian time underlies the faint young Sun paradox, described into the section Climates of early Earth.

Radiative energy from the Sun is variable at very small timescales, owing to solar storms and other disturbances, but variations in solar activity, particularly the frequency of sunspots, may also be documented at decadal to millennial timescales and probably occur at longer timescales as well. The ‘Maunder minimum,’ a period of drastically paid off sunspot activity between AD 1645 and 1715, was suggested as being a contributing factor to the Little Ice Age. (See below Climatic variation and change since the emergence of civilization.)

The sun’s rays as imaged in extreme ultraviolet light by the Earth-orbiting Solar and Heliospheric Observatory (SOHO) satellite. A massive loop-shaped eruptive prominence is visible at the lower left. Nearly white areas are the hottest; deeper reds indicate cooler temperatures.NASA

Volcanic activity

Volcanic activity can influence climate in a number of methods at different timescales. Individual volcanic eruptions can release large quantities of sulfur dioxide and other aerosols into the stratosphere, reducing atmospheric transparency and thus the total amount of solar radiation reaching Earth’s surface and troposphere. a recent example is the 1991 eruption in the Philippines of Mount Pinatubo, which had measurable influences on atmospheric blood flow and heat budgets. The 1815 eruption of Mount Tambora regarding the island of Sumbawa had more dramatic consequences, whilst the spring and summer of the following year (1816, known as ‘the year without a summer’) were unusually cold over much of the world. New England and Europe experienced snowfalls and frosts through the entire summer of 1816.

Mount PinatuboA column of gas and ash rising from Mount Pinatubo into the Philippines on June 12, 1991, just days before the volcano’s climactic explosion on June 15.David H. Harlow/U.S.Geological Survey

Volcanoes and related phenomena, such as for example ocean rifting and subduction, release skin tightening and into both the oceans additionally the atmosphere. Emissions are low; even a massive volcanic eruption such as Mount Pinatubo releases just a fraction of the skin tightening and emitted by fossil-fuel combustion in a year. At geologic timescales, nonetheless, release of this greenhouse gas may have important effects. Variations in carbon dioxide release by volcanoes and ocean rifts over millions of years can alter the chemistry of the atmosphere. Such changeability in carbon dioxide concentrations probably accounts for much of the climatic variation that has taken destination during the Phanerozoic Eon. (See below Phanerozoic climates.)

Tectonic activity

continental driftThe changing Earth through geologic time, from the late Cambrian Period (c. 500 million years ago) to the projected period of ‘Pangea Proxima’ (c. 250 million years from now). The locations with time of the present-day continents are shown in the inset.Adapted from C.R. Scotese, The University of Texas at ArlingtonSee all videos for this article

Tectonic movements of Earth’s crust have had profound effects on climate at timescales of millions to tens of years. These movements have changed the shape, size, position, and elevation of the continental masses as well as the bathymetry of the oceans. Topographic and bathymetric changes in turn have had strong effects regarding the blood flow of both the atmosphere additionally the oceans. For example, the uplift of the Tibetan Plateau during the Cenozoic Era affected atmospheric blood flow patterns, creating the South Asian monsoon and influencing climate over much of the rest of Asia and neighbouring regions.

Tectonic activity also influences atmospheric chemistry, particularly carbon dioxide concentrations. Skin tightening and is emitted from volcanoes and vents in rift zones and subduction zones. Variations into the rate of spreading in rift zones additionally the degree of volcanic activity near plate margins have influenced atmospheric skin tightening and concentrations throughout Earth’s history. Even the chemical weathering of rock constitutes a important sink for skin tightening and. (A carbon sink is any process that removes carbon dioxide from the atmosphere by the chemical conversion of CO2 to organic or inorganic carbon compounds.) Carbonic acid, formed from carbon dioxide and water, is a reactant in dissolution of silicates and other minerals. Weathering rates are related to the mass, elevation, and exposure of bedrock. Tectonic uplift can increase all these elements and thus result in increased weathering and carbon dioxide absorption. For example, the chemical weathering of the rising Tibetan Plateau may have played a important role in depleting the atmosphere of skin tightening and during a global cooling period into the late Cenozoic Era. (See below Cenozoic climates.)

Orbital (Milankovich) variations

The orbital geometry of Earth is affected in predictable methods https://shmoop.pro/as-you-like-it-by-william-shakespeare-summary/ by the gravitational influences of other planets into the solar system. Three primary features of Earth’s orbit are affected, each in a cyclic, or regularly recurring, manner. First, the shape of Earth’s orbit round the Sun, varies from nearly circular to elliptical (eccentric), with periodicities of 100,000 and 413,000 years. Second, the tilt of Earth’s axis with respect to the Sun, which is primarily responsible for Earth’s seasonal climates, varies between 22.1° and 24.5° from the plane of Earth’s rotation round the Sun. This variation takes place on a cycle of 41,000 years. In general, the greater the tilt, the greater the solar radiation received by hemispheres in summer additionally the less received in winter months. The third cyclic change to Earth’s orbital geometry results from two blended phenomena: (1) Earth’s axis of rotation wobbles, changing the path of the axis with respect to the Sun, and (2) the orientation of Earth’s orbital ellipse rotates slowly. These two processes create a 26,000-year cycle, called precession of the equinoxes, in which the position of Earth at the equinoxes and solstices changes. Today Earth is closest towards the Sun (perihelion) near the December solstice, whereas 9,000 years ago perihelion occurred near the June solstice.

These orbital variations cause changes in the latitudinal and seasonal distribution of solar radiation, which in turn drive a number of climate variations. Orbital variations play major roles in pacing glacial-interglacial and monsoonal patterns. Their influences being identified in climatic changes over much of the Phanerozoic. For example, cyclothems—which are interbedded marine, fluvial, and coal beds characteristic of the Pennsylvanian Subperiod (318.1 million to 299 million years ago)—appear to represent Milankovitch-driven changes in mean sea level.

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• Iceberg: Climatic impacts of icebergs
• Tundra: Effects of real human activities and climate change

Greenhouse gases

greenhouse effectThe greenhouse effect is caused by the atmospheric accumulation of gases such as carbon dioxide and methane, which contain some of the heat emitted from Earth’s surface.Created and created by QA International. © QA International, 2010. All rights reserved. www.qa-international.comSee all videos for this article

Greenhouse gases are gas molecules that have the property of absorbing infrared radiation (net heat energy) emitted from Earth’s surface and reradiating it back to Earth’s surface, thus causing the phenomenon known as the greenhouse effect. Skin tightening and, methane, and water vapour are the most important greenhouse gases, and they have a profound effect on the energy budget of the Earth system despite making up just a fraction of all atmospheric gases. Concentrations of greenhouse gases have varied substantially during Earth’s history, and these variations have driven substantial climate changes at a wide range of timescales. In general, greenhouse gas concentrations have already been specially high during warm periods and low during cold phases. A number of processes influence greenhouse gas concentrations. Some, such as for example tectonic activities, work at timescales of years, whereas others, such as for example vegetation, soil, wetland, and ocean sources and sinks, work at timescales of hundreds to thousands of years. Individual activities—especially fossil-fuel combustion since the Industrial Revolution—are responsible for steady increases in atmospheric concentrations of various greenhouse gases, specially carbon dioxide, methane, ozone, and chlorofluorocarbons (CFCs).

greenhouse effect on EarthThe greenhouse effect on Earth. Some incoming sunlight is reflected by Earth’s atmosphere and surface, but most is absorbed by the surface, which is warmed. Infrared (IR) radiation is then emitted from the surface. Some IR radiation escapes to space, but some is absorbed by the atmosphere’s greenhouse gases (especially water vapour, skin tightening and, and methane) and reradiated in all directions, some to space and some back toward the outer lining, where it further warms the outer lining additionally the lower atmosphere.Encyclopædia Britannica, Inc.
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climate: El Niño/Southern Oscillation and climatic change
As was explained earlier, the oceans can moderate the climate of certain regions. Not only do they affect such geographic variations, but…

Feedback

Perhaps the most intensively discussed and researched topic in climate variability is the role of interactions and feedbacks among the various components of the Earth system. The feedbacks involve different components that work at different rates and timescales. Ice sheets, sea ice, terrestrial vegetation, ocean temperatures, weathering rates, ocean blood flow, and greenhouse gas concentrations are all influenced either directly or indirectly by the atmosphere; nonetheless, they also all feed back into the atmosphere, thereby influencing it in important methods. For example, different forms and densities of vegetation regarding the land surface influence the albedo, or reflectivity, of Earth’s surface, thus affecting the overall radiation budget at local to regional scales. At the same time climate change composition writing, the transfer of water molecules from soil towards the atmosphere is mediated by vegetation, both directly (from transpiration through plant stomata) and indirectly (from shading and temperature influences on direct evaporation from soil). This regulation of latent heat flux by vegetation can influence climate at local to global scales. As being a result, changes in vegetation, which are partially controlled by climate, can in turn influence the climate system. Vegetation also influences greenhouse gas concentrations; living plants constitute an important sink for atmospheric skin tightening and, whereas they behave as resources of skin tightening and when they are burned by wildfires or undergo decomposition. These and other feedbacks on the list of various components of the Earth system are critical for both understanding past climate changes and predicting future ones.

Mixed evergreen and hardwood forest regarding the slopes of the Adirondack Mountains near Keene Valley, New York.Jerome Wyckoff
Surface reflectance (albedo) of solar energy under different patterns of land use. (Left) In a preagricultural landscape, large forest-covered areas of low surface albedo alternate with large open areas of high albedo. (Right) In a agricultural landscape, a patchwork of smaller forested and open areas exists, each with its characteristic albedo.Encyclopædia Britannica, Inc.

Individual activities

Recognition of global climate change as an environmental issue has drawn attention to the climatic impact of real human activities. Nearly all of this attention has focused on skin tightening and emission via fossil-fuel combustion and deforestation. Individual activities also yield releases of other greenhouse gases, such as for example methane (from rice cultivation, livestock, landfills, and other sources) and chlorofluorocarbons (from manufacturing sources). There is little doubt among climatologists that these greenhouse gases affect the radiation budget of Earth; the nature and magnitude of the climatic response are a subject of intense research activity. Paleoclimate records from tree rings, coral, and ice cores indicate a clear warming trend spanning the entire 20th century additionally the first decade of the 21st century. In fact, the 20th century was the warmest of the past 10 centuries, additionally the decade 2001–10 was the warmest decade since the beginning of modern instrumental record keeping. Many climatologists have pointed to this warming pattern as clear evidence of human-induced climate change resulting from the production of greenhouse gases.

The global average surface temperature range for each year from 1861 to 2000 is shown by solid red bars, with the confidence range into the data for each year shown by thin whisker bars. The average change over time is shown by the solid curve.Encyclopædia Britannica, Inc.

An extra kind of real human impact, the conversion of vegetation by deforestation, afforestation, and agriculture, is receiving mounting attention as a further source of climate change. It really is becoming increasingly clear that human impacts on vegetation cover may have local, regional, and even global effects on climate, due to changes in the sensible and latent heat flux towards the atmosphere additionally the distribution of energy within the climate system. The extent to which these elements subscribe to recent and ongoing climate change is an important, emerging area of study.

Tropical forests and deforestationTropical forests and deforestation in the early 21st century.Encyclopædia Britannica, Inc.

Climate Change Within A Human Life Span

Irrespective of their locations on the planet, all humans experience climate variability and change of their lifetimes. The most familiar and predictable phenomena are the seasonal cycles, to which men and women adjust their clothing, outdoor activities, thermostats, and agricultural practices. Nonetheless, no two summers or winters are exactly alike into the same destination; some are warmer, wetter, or stormier than others. This interannual variation in climate is partly responsible for year-to-year variations in fuel prices, crop yields, road maintenance budgets, and wildfire hazards. Single-year, precipitation-driven floods could cause severe economic damage, such as those of the upper Mississippi River drainage basin during the summer of 1993, and loss of life, such as those that devastated much of Bangladesh in the summer of 1998. Similar damage and loss of life can also occur as the result of wildfires, severe storms, hurricanes, heat waves, and other climate-related events.

Climate variation and change may also occur over longer periods, such as for example decades. Some locations experience multiple years of drought, floods, or other harsh conditions. Such decadal variation of climate poses challenges to real human activities and planning. For example, multiyear droughts can disrupt water supplies, induce crop failures, and cause economic and social dislocation, as with the situation of the Dust Bowl droughts into the midcontinent of North America during the 1930s. Multiyear droughts may even cause widespread starvation, as with the Sahel drought that occurred in northern Africa during the 1970s and ’80s.

Abandoned farmstead showing the effects of wind erosion into the Dust Bowl, Texas county, Okla., 1937.USDA Photo

Seasonal variation

Every place on Earth experiences seasonal variation in climate ( though the shift can be slight in some tropical regions). This cyclic variation is driven by seasonal changes in the availability of solar radiation to Earth’s atmosphere and surface. Earth’s orbit round the Sun is elliptical; it is closer to the sun’s rays ( 147 million km [about 91 million miles]) near the winter solstice and farther from the Sun (152 million km [about 94 million miles]) near the summer solstice in the Northern Hemisphere. Also, Earth’s axis of rotation takes place at an oblique angle (23.5°) with respect to its orbit. Thus, each hemisphere is tilted away from the Sun during its winter period and toward the sun’s rays in its summer period. When a hemisphere is tilted away from the Sun, it receives less solar radiation than the contrary hemisphere, which during those times is pointed toward the sun’s rays. Thus, despite the closer proximity of the Sun at the winter solstice, the Northern Hemisphere receives less solar radiation during the winter than it does during the summer. Also as a consequence of the tilt, whenever Northern Hemisphere experiences winter, the Southern Hemisphere experiences summer.

A diagram shows the position of Earth at the beginning of each season in the Northern Hemisphere.Encyclopædia Britannica, Inc.

Earth’s climate system is driven by solar radiation; seasonal differences in climate ultimately result from the seasonal changes in Earth’s orbit. The blood flow of air into the atmosphere and water into the oceans responds to seasonal variations of available energy from the Sun. Specific seasonal changes in climate occurring at any given location on Earth’s surface largely result from the transfer of energy from atmospheric and oceanic blood flow. Differences in surface heating taking place between summer and cold weather cause storm tracks and pressure centres to shift position and strength. These heating differences also drive seasonal changes in cloudiness, precipitation, and wind.

Seasonal responses of the biosphere (especially vegetation) and cryosphere (glaciers, sea ice, snowfields) also feed into atmospheric blood flow and climate. Leaf fall by deciduous trees as they go into winter dormancy advances the albedo (reflectivity) of Earth’s surface that will lead to greater local and regional cooling. Similarly, snow accumulation also advances the albedo of land surfaces and often amplifies winter’s effects.