Skip Nav

Global warming

Navigation menu

❶Will the Recession Kill Recycling?

global warming

Term Lookup
Climatic variation since the last glaciation

Sixty-two percent said the effects of global warming had already begun while 42 percent said it posed a "serious threat. In New York, where irony pulses through the culture, people ask, "If there is global warming , why is it so cold? If global warming predicts "a catastrophy of cold and hot, drought and flood", then can the great Australian droughts of the 19th century be blamed on global warming?

Global warming too convenient; Letters. Turning up the heat: An overwhelming majority of the articles from the New York Times 94 percent and the Globe and Mail 96 percent were identified as accepting catastrophic global warming as a reality.

Bias in media coverage: Such a major issue deserves more unbiased, objective reporting. The Bush administration has been skeptical about the causes of global warming. Bush has not acknowledged global warming as a problem. The warmest year on the record: Will be even hotter? It also predicted, again depending on a wide range of scenarios, that by the end of the 21st century the global average sea level could rise by another 29—95 cm The scenarios referred to above depend mainly on future concentrations of certain trace gases, called greenhouse gases , that have been injected into the lower atmosphere in increasing amounts through the burning of fossil fuels for industry, transportation , and residential uses.

In the IPCC reported that concentrations of carbon dioxide, methane, and nitrous oxides in the atmosphere surpassed those found in ice cores dating back , years. Of all these gases, carbon dioxide is the most important, both for its role in the greenhouse effect and for its role in the human economy. It has been estimated that, at the beginning of the industrial age in the midth century, carbon dioxide concentrations in the atmosphere were roughly parts per million ppm.

By the middle of , carbon dioxide concentrations had briefly reached ppm, and, if fossil fuels continue to be burned at current rates, they are projected to reach ppm by the midst century—essentially, a doubling of carbon dioxide concentrations in years.

A vigorous debate is in progress over the extent and seriousness of rising surface temperatures, the effects of past and future warming on human life, and the need for action to reduce future warming and deal with its consequences. This article provides an overview of the scientific background and public policy debate related to the subject of global warming.

It considers the causes of rising near-surface air temperatures, the influencing factors, the process of climate research and forecasting, the possible ecological and social impacts of rising temperatures, and the public policy developments since the midth century.

Global warming is related to the more general phenomenon of climate change, which refers to changes in the totality of attributes that define climate. Normally, climate change can be viewed as the combination of various natural forces occurring over diverse timescales. The term global warming is used specifically to refer to any warming of near-surface air during the past two centuries that can be traced to anthropogenic causes. To define the concepts of global warming and climate change properly, it is first necessary to recognize that the climate of Earth has varied across many timescales, ranging from an individual human life span to billions of years.

Worldwide, the most recent glacial period, or ice age , culminated about 21, years ago in what is often called the Last Glacial Maximum.

During this time, continental ice sheets extended well into the middle latitude regions of Europe and North America , reaching as far south as present-day London and New York City. It is important to remember that these figures are a global average. This glacial interval terminated abruptly about 11, years ago and was followed by the subsequent relatively ice-free period known as the Holocene Epoch.

However, some scientists have argued that the Holocene Epoch terminated in the relatively recent past and that Earth currently resides in a climatic interval that could justly be called the Anthropocene Epoch—that is, a period during which humans have exerted a dominant influence over climate.

Though less dramatic than the climate changes that occurred during the Pleistocene Epoch , significant variations in global climate have nonetheless taken place over the course of the Holocene. During the early Holocene, roughly 9, years ago, atmospheric circulation and precipitation patterns appear to have been substantially different from those of today.

For example, there is evidence for relatively wet conditions in what is now the Sahara Desert. During the middle Holocene, some 5,—7, years ago, conditions appear to have been relatively warm—indeed, perhaps warmer than today in some parts of the world and during certain seasons. For this reason, this interval is sometimes referred to as the Mid-Holocene Climatic Optimum.

The relative warmth of average near-surface air temperatures at this time, however, is somewhat unclear. Changes in the pattern of insolation favoured warmer summers at higher latitudes in the Northern Hemisphere, but these changes also produced cooler winters in the Northern Hemisphere and relatively cool conditions year-round in the tropics.

Any overall hemispheric or global mean temperature changes thus reflected a balance between competing seasonal and regional changes. In fact, recent theoretical climate model studies suggest that global mean temperatures during the middle Holocene were probably 0. Over subsequent millennia, conditions appear to have cooled relative to middle Holocene levels. We welcome suggested improvements to any of our articles. You can make it easier for us to review and, hopefully, publish your contribution by keeping a few points in mind.

Your contribution may be further edited by our staff, and its publication is subject to our final approval. Unfortunately, our editorial approach may not be able to accommodate all contributions. Our editors will review what you've submitted, and if it meets our criteria, we'll add it to the article. Please note that our editors may make some formatting changes or correct spelling or grammatical errors, and may also contact you if any clarifications are needed.

Henrik Selin Michael E. Sep 13, See Article History. Page 1 of Next page Causes of global warming. Learn More in these related Britannica articles:

GLOBAL WARMING Defined for English Language Learners

Main Topics

Privacy Policy

Global warming, also referred to as climate change, is the observed century-scale rise in the average temperature of the Earth's climate system and its related effects. Multiple lines of scientific evidence show that the climate system is warming.

Privacy FAQs

Global warming definition is - an increase in the earth's atmospheric and oceanic temperatures widely predicted to occur due to an increase in the greenhouse effect resulting especially from pollution.

About Our Ads

Expected long-term effects of current global warming are rising sea levels, flooding, melting of polar ice caps and glaciers, fluctuations in temperature and precipitation, more frequent and stronger El Niños and La Niñas, drought, heat waves, and forest fires. See more at greenhouse effect. Jun 23,  · Global warming: the increase in Earth’s average surface temperature due to rising levels of greenhouse gases. Climate change: a long-term change in the Earth’s climate, or of a region on Earth. Within scientific journals, this .

Cookie Info

A: Global warming occurs when carbon dioxide (CO2) and other air pollutants and greenhouse gases collect in the atmosphere and absorb sunlight and solar radiation that have bounced off the earth. As the name suggests, 'global warming' refers to the long-term trend of a rising average global temperature, which you can see here: 'Climate change', again as the name suggests, refers to the changes in the global climate which result from the increasing average global temperature.