Climate change
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What is climate change?
Climate change refers to long-term shifts in temperatures and weather patterns. While these shifts can occur naturally, human activities, primarily the burning of fossil fuels like coal, oil, and gas, have been the main driver since the 1800s. This human-caused change encompasses global warming, which is the increase in average air temperatures, but also includes broader changes like rising sea levels and melting glaciers. These changes are largely due to increased greenhouse gases in the atmosphere.
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What causes climate change?
Climate change is primarily caused by human activities that increase the concentration of greenhouse gases in the Earth's atmosphere. The combustion of fossil fuels and deforestation are major contributors to the release of carbon dioxide (CO2), a significant greenhouse gas. Other human activities, such as rice cultivation, livestock farming, and industrial processes, release methane (CH4) and fluorinated gases, which also trap heat.
These increased greenhouse gas concentrations enhance the greenhouse effect, leading to a warming trend observed over the past century. Changes in land use, such as converting forests to agriculture, also influence climate by altering the Earth's surface reflectivity and heat exchange with the atmosphere. While natural factors can influence climate, the current warming trend is overwhelmingly attributed to human-induced emissions.
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What are greenhouse gases?
Greenhouse gases are atmospheric gases that absorb and reradiate heat energy emitted from Earth's surface, contributing to the greenhouse effect. This natural process keeps the planet warm enough to support life.
The most significant greenhouse gases include:
* Water vapor: The most potent, its concentration is influenced by air temperature.
* Carbon dioxide (CO₂): A major contributor, increased by human activities like burning fossil fuels and deforestation.
* Methane (CH₄): More potent than CO₂ but less concentrated, emitted from sources like livestock farming and natural gas leaks.
* Ozone (O₃): Specifically surface-level ozone, resulting from air pollution.
* Nitrous oxides (N₂O) and fluorinated gases: Primarily produced by industrial activities.Human activities, particularly the combustion of fossil fuels since the Industrial Revolution, have significantly increased the concentrations of these gases, intensifying the greenhouse effect and driving climate change.
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How does climate change affect weather patterns?
Climate change significantly alters weather patterns, making them more extreme and unstable. Global warming leads to shifts in precipitation, with increased rainfall expected in polar and subpolar regions, while middle latitudes may experience decreased precipitation due to poleward shifts in jet streams. Equatorial regions are predicted to see more rainfall, contrasting with a decrease in subtropical areas.
These changes can result in a higher probability of both droughts and floods in various regions. Additionally, rising ocean temperatures associated with global warming may lead to more intense tropical cyclones, such as hurricanes. While the exact impact on the frequency of these storms is still debated, the intensity of those that do form is expected to increase.
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What are some effects of climate change on animals and plants?
Climate change poses significant threats to plants and animals. Rising global temperatures can alter established seasonal patterns, impacting processes like leaf production and migration timing for birds and fish. Species may face increased extinction risks as their natural adaptive capacities are challenged by rapid climatic shifts. Ocean acidification, caused by increased carbon dioxide absorption, reduces carbonate ions essential for shell and skeleton formation in marine life like corals and shellfish. This can lead to smaller organisms, increased vulnerability to predators, and even dissolution of shells. Furthermore, changes in sea ice affect high-latitude predators such as polar bears and walruses. Extreme weather events, intensified by climate change, also cause direct mortality and habitat destruction for various species.
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What can people do to slow down climate change?
To slow climate change, individuals can reduce their carbon footprint by adopting energy-efficient practices at home, such as improving insulation and using less energy for heating and cooling. They can also opt for renewable energy sources for household electricity and choose more energy-efficient vehicles like electric or hybrid cars, or utilize public transportation. Additionally, making conscious purchasing decisions for more sustainable products and reducing meat consumption can contribute to lowering secondary carbon footprints.
Globally, mitigation policies focus on reducing greenhouse gas emissions by transitioning to less carbon-intensive energy sources like wind, solar, and hydropower, and by improving energy efficiency in transportation and developing technologies such as carbon capture and storage.
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News •
Climate change, periodic modification of Earth’s climate brought about as a result of changes in the atmosphere as well as interactions between the atmosphere and various other geologic, chemical, biological, and geographic factors within the Earth system.
The atmosphere is a dynamic fluid that is continually in motion. Both its physical properties and its rate and direction of motion are influenced by a variety of factors, including solar radiation, the geographic position of continents, ocean currents, the location and orientation of mountain ranges, atmospheric chemistry, and vegetation growing on the land surface. All these factors change through time. Some factors, such as the distribution of heat within the oceans, atmospheric chemistry, and surface vegetation, change at very short timescales. Others, such as the position of continents and the location and height of mountain ranges, change over very long timescales. Therefore, climate, which results from the physical properties and motion of the atmosphere, varies at every conceivable timescale.
Climate is often defined loosely as the average weather at a particular place, incorporating such features as temperature, precipitation, humidity, and windiness. A more specific definition would state that climate is the mean state and variability of these features over some extended time period. Both definitions acknowledge that the weather is always changing, owing to instabilities in the atmosphere. And as weather varies from day to day, so too does climate vary, from daily day-and-night cycles up to periods of geologic time hundreds of millions of years long. In a very real sense, climate variation is a redundant expression—climate is always varying. No two years are exactly alike, nor are any two decades, any two centuries, or any two millennia.
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This article addresses the concept of climatic variation and change within the set of integrated natural features and processes known as the Earth system. The nature of the evidence for climate change is explained, as are the principal mechanisms that have caused climate change throughout the history of Earth. Finally, a detailed description is given of climate change over many different timescales, ranging from a typical human life span to all of geologic time. For a detailed description of the development of Earth’s atmosphere, see the article atmosphere, evolution of. For full treatment of the most critical issue of climate change in the contemporary world, see global warming.
The Earth system
The atmosphere is influenced by and linked to other features of Earth, including oceans, ice masses (glaciers and sea ice), land surfaces, and vegetation. Together, they make up an integrated Earth system, in which all components interact with and influence one another in often complex ways. For instance, climate influences the distribution of vegetation on Earth’s surface (e.g., deserts exist in arid regions, forests in humid regions), but vegetation in turn influences climate by reflecting radiant energy back into the atmosphere, transferring water (and latent heat) from soil to the atmosphere, and influencing the horizontal movement of air across the land surface.
Earth scientists and atmospheric scientists are still seeking a full understanding of the complex feedbacks and interactions among the various components of the Earth system. This effort is being facilitated by the development of an interdisciplinary science called Earth system science. Earth system science is composed of a wide range of disciplines, including climatology (the study of the atmosphere), geology (the study of Earth’s surface and underground processes), ecology (the study of how Earth’s organisms relate to one another and their environment), oceanography (the study of Earth’s oceans), glaciology (the study of Earth’s ice masses), and even the social sciences (the study of human behaviour in its social and cultural aspects).
A full understanding of the Earth system requires knowledge of how the system and its components have changed through time. The pursuit of this understanding has led to development of Earth system history, an interdisciplinary science that includes not only the contributions of Earth system scientists but also paleontologists (who study the life of past geologic periods), paleoclimatologists (who study past climates), paleoecologists (who study past environments and ecosystems), paleoceanographers (who study the history of the oceans), and other scientists concerned with Earth history. Because different components of the Earth system change at different rates and are relevant at different timescales, Earth system history is a diverse and complex science. Students of Earth system history are not just concerned with documenting what has happened; they also view the past as a series of experiments in which solar radiation, ocean currents, continental configurations, atmospheric chemistry, and other important features have varied. These experiments provide opportunities to learn the relative influences of and interactions between various components of the Earth system. Studies of Earth system history also specify the full array of states the system has experienced in the past and those the system is capable of experiencing in the future.
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Undoubtedly, people have always been aware of climatic variation at the relatively short timescales of seasons, years, and decades. Biblical scripture and other early documents refer to droughts, floods, periods of severe cold, and other climatic events. Nevertheless, a full appreciation of the nature and magnitude of climatic change did not come about until the late 18th and early 19th centuries, a time when the widespread recognition of the deep antiquity of Earth occurred. Naturalists of this time, including Scottish geologist Charles Lyell, Swiss-born naturalist and geologist Louis Agassiz, English naturalist Charles Darwin, American botanist Asa Gray, and Welsh naturalist Alfred Russel Wallace, came to recognize geologic and biogeographic evidence that made sense only in the light of past climates radically different from those prevailing today.
Geologists and paleontologists in the 19th and early 20th centuries uncovered evidence of massive climatic changes taking place before the Pleistocene—that is, before some 2.6 million years ago. For example, red beds indicated aridity in regions that are now humid (e.g., England and New England), whereas fossils of coal-swamp plants and reef corals indicated that tropical climates once occurred at present-day high latitudes in both Europe and North America. Since the late 20th century the development of advanced technologies for dating rocks, together with geochemical techniques and other analytical tools, have revolutionized the understanding of early Earth system history.
The occurrence of multiple epochs in recent Earth history during which continental glaciers, developed at high latitudes, penetrated into northern Europe and eastern North America was recognized by scientists by the late 19th century. Scottish geologist James Croll proposed that recurring variations in orbital eccentricity (the deviation of Earth’s orbit from a perfectly circular path) were responsible for alternating glacial and interglacial periods. Croll’s controversial idea was taken up by Serbian mathematician and astronomer Milutin Milankovitch in the early 20th century. Milankovitch proposed that the mechanism that brought about periods of glaciation was driven by cyclic changes in eccentricity as well as two other orbital parameters: precession (a change in the directional focus of Earth’s axis of rotation) and axial tilt (a change in the inclination of Earth’s axis with respect to the plane of its orbit around the Sun). Orbital variation is now recognized as an important driver of climatic variation throughout Earth’s history (see below Orbital [Milankovitch] variations).