Climate Change, Effects

CLIMATE CHANGE IS commonly used to describe any systematic alteration or statistically significant variation in either the average state of the climate elements such as precipitation, temperature, winds, or pressure; or in its variability, sustained over a finite time period (decades or longer). It can be referred to as the long-term change in global weather patterns, associated especially with increases in temperature, precipitation, and storm activity.

These inconsistencies in climate systems are a potential consequence of the greenhouse effect by greenhouse gases (GHGs). Examples of greenhouse gases include: carbon dioxide (CO2), methane (CH4), dinitrogen monoxide or nitrous oxide (N2O), halocarbon gases such as trichlorofluorocarbon (CFQ3) and dichloroflurocarbon (CF2C12), water (H2O), perfluorocarbons (PFCs), and sulfur hexafluoride (SF6). The atmospheric concentrations of these gases have been increasing, due to anthropogenic activities.

Climate change is attributed directly or indirectly to anthropogenic activities that impact the natural composition of the global climate elements. It may also be a result of natural external forcing, such as changes in Earths orbital variables, or solar emission, and other natural internal processes of the Earth's climate system. The relative influences of external anthropogenic and natural factors on climate can be broadly compared, using the concept of radiative forcing. Radiative forcing simply refers to the process that disrupts the infrared radiation balance between incoming solar radiation from the Sun and the outgoing radiation from the Earth. A positive radiative forcing primarily results in the relative warming of the Earths surface and is due to increasing levels of GHGs. A negative radiative forcing, which can arise from an increase in some types of aerosols, tends to bring about the cooling of the Earth's surface.

Changes in orbital variables, solar output, or explosive volcanic activity, are natural external factors that can also cause radiative forcing. The systematic account of these climate-forcing agents and their differences over a timescale is required to understand past climate changes in the context of natural variations, and to predict the nature of future climate changes.

The effects of climate change include variations in biospheric ambient temperature, which could lead to heat stress, change in rainfall patterns, sea-level rise, saltwater intrusion, loss of biodiversity, drought, habitat loss, and freshwater depletion and pollution. In most cases, climate change has been used interchangeably with global warming, and the greenhouse effect. However, in recent accepted usage, climate change only connotes any change or changes in modern climate systems, whether due to natural variability or as a result of human-caused activity, including an increase over a period of time of the average temperature of the Earth's atmosphere and oceans, known as global warming.

The United Nations Framework Convention on Climate Change (UNFCCC) has adopted the phrase climate variability for non-human mediated changes in climate elements. Climate variability is usually natural in origin, resulting primarily from slight variations in the complex processes that drive the movement of heat and mass between the atmosphere, the marine aquatic ecosystems, and the land surfaces. For example, the El Nino-Southern Oscillation (ENSO) is caused by weakening trade winds in the southern part of the Pacific Ocean, and has consistently affected regional variations of precipitation and temperature over much of the tropics, subtropics, and some mid-latitude areas, leading to warmer episodes in these areas. Trade winds carry warmer air west, which leads to rising sea temperatures and increased precipitation.

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