Climate Change , the Fourth Assessment Report (AR4) of the United Nations .. at the Wayback Machine., p. 5, and figure SPM.3, in IPCC AR4 WG1 ipcc-ar4-wg1, Climate Change The Physical Science Basis. Contribution of Working Group I to the Fourth Assessment Report of the Intergovernmental. Coordinating Lead Authors: Piers Forster (UK), Venkatachalam Ramaswamy (USA). Lead Authors: Paulo Artaxo (Brazil), Terje Berntsen (Norway), Richard Betts.


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It looked at the ability of science to attribute ipcc ar4 wg1 to different causes, and made projections of future climate change. It was produced by authors lead authors, 26 review editors, and contributing authors from 40 countries, then reviewed by over expert reviewers.

IPCC Fourth Assessment Report - Wikipedia

More than 6, peer-reviewed publications were cited. Changes in the atmosphere[ edit ] Carbon dioxidemethaneand nitrous oxide are all long-lived greenhouse gases. How much each contributes is not well determined. More than a third of this rise is due to human activity, primarily agriculture.

Hot days, hot nights, and heat waves have become more frequent. Eleven of the twelve years in the period — rank among the top 12 warmest ipcc ar4 wg1 in the instrumental record since Ipcc ar4 wg1 in the last years has caused about a 0.


This is up from the 0. Urban heat island effects were determined to have negligible influence less than 0.


Average Northern Hemisphere temperatures during the second half ipcc ar4 wg1 the 20th century were very likely higher than ipcc ar4 wg1 any other year period in the last years and likely the highest in at least the past years including both the Medieval Warm Period and the Little Ice Age. Ice, snow, permafrost, rain, and the oceans[ edit ] The SPM documents increases in wind intensity, decline of permafrost coverage, and increases of both drought and heavy precipitation events.

Ocean warming causes seawater to expand, which contributes to sea level rising. Sea level rose at an average rate of about 1. The rise in sea level during — was at an ipcc ar4 wg1 rate of 3.

Chapter 2: Changes in Atmospheric Constituents and in Radiative Forcing

It is not clear whether ipcc ar4 wg1 is a long-term trend or just variability. Antarctic sea ice shows no significant overall trend, ipcc ar4 wg1 with a lack of warming in that region. Hurricanes[ edit ] There has been an increase in hurricane intensity in the North Atlantic since the s, and that increase correlates with increases in sea surface temperature.

The observed increase in hurricane intensity is larger than climate models predict for the sea surface temperature changes we have experienced. There is no clear trend in the number of hurricanes.

Chapter 2: Changes in Atmospheric Constituents and in Radiative Forcing - AR4 WGI

Other regions appear to have experienced increased hurricane intensity as well, but there are concerns about the quality of data in these other regions.

Table SPM-2 lists recent trends along with certainty levels for the trend having actually occurred, for a human contribution to the trend, and for the ipcc ar4 wg1 occurring in the future.

In relation to changes including increased hurricane ipcc ar4 wg1 where the certainty of a human contribution is stated as "more likely than not" footnote f to table SPM-2 notes "Magnitude of anthropogenic contributions not assessed.

Attribution for these phenomena based on expert judgment rather than formal attribution studies.


The report shows in detail the individual warming contributions positive forcing of carbon dioxide, methane, nitrous oxide, halocarbonsother human warming factors, and the warming effects of changes in solar activity.

Also shown are the cooling effects negative forcing of aerosolsland-use changes, and ipcc ar4 wg1 human activities. All values ipcc ar4 wg1 shown as a change from pre-industrial conditions.

Climate sensitivity[ edit ] Climate sensitivity is defined as the amount of global average surface warming following a doubling of carbon dioxide concentrations. As a result, predictions for the 21st century are as shown below.