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Topic: Climate forcings

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	NASA GISS: Science Briefs: Forcings and Chaos in Global Climate Change (Site not responding. Last check: 2007-10-25)
		And it can generate more ensembles in which climate forcings, such as volcanos and greenhouse gases, are added to the model one-by-one to study their effects.
		The Pinatubo team found that when the model is subject to measured climate forcings, namely greenhouse gases such as CO, volcanic aerosols, ozone depletion, and solar radiation changes, the model yields a global average temperature change similar to that observed.
		Forcings such as greenhouse gases, on the average, alter temperature over two decades by only a few tenths of a degree, while chaotic fluctuations are several times larger.
	www.giss.nasa.gov /research/briefs/hansen_03 (828 words)

	NOAA Paleoclimatology Global Warming - The Story
		Climate is the weather pattern we expect over the period of a month, a season, a decade, or a century.
		More technically, climate is defined as the weather conditions resulting from the mean, or average, state of the atmosphere-ocean-land system, often described in terms of "climate normals" or average weather conditions.
		Annual records of climate are preserved in tree-rings, locked in the skeletons of tropical coral reefs, frozen in glaciers and ice caps, and buried in the sediments of lakes and oceans.
	www.ncdc.noaa.gov /paleo/globalwarming/paleo.html (800 words)

	Top Story - AN ALTERNATE SCENARIO FOR CLIMATE CHANGE
		Although the sum of all forcings coincidentally is similar to that for carbon dioxide alone, knowledge of each of the large forcings such as methane and fl carbon (soot) is needed for development of effective policies.
		Climate forcings, or factors that promote warming, such as emissions of carbon dioxide (CO2), methane (CH4), nitrous oxide (N20) and chlorofluorocarbons (CFCs) have increased in the world's atmosphere since the technology of the industrial revolution began pumping these into the atmosphere beginning in the 1800s.
		In the graph, climate forcings due to CO2 increases are depicted in light blue, CH4 in dark blue, N20 in yellow, and CFCs in red.
	www.gsfc.nasa.gov /topstory/20020103greenhouse.html (1722 words)

	Climate Change 2001: The Scientific Basis
		This represents our subjective judgement about the reliability of the forcing estimate, involving factors such as the assumptions necessary to evaluate the forcing, the degree of our knowledge of the physical/chemical mechanisms determining the forcing, and the uncertainties surrounding the quantitative estimate of the forcing (see Table 6.12).
		The forcing associated with stratospheric aerosols from volcanic eruptions is highly variable over the period and is not considered for this plot (however, see Figure 6.8d).
		All the forcings shown have distinct spatial and seasonal features (Figure 6.7) such that the global, annual means appearing on this plot do not yield a complete picture of the radiative perturbation.
	www.grida.no /climate/ipcc_tar/wg1/fig6-6.htm (491 words)

	NASA GISS: Science Briefs: Climate Forcings in the Industrial Era (Site not responding. Last check: 2007-10-25)
		Climate sensitivity is still an important topic, but we maintain that convincing evidence has accumulated in the past 20 years that climate is indeed very sensitive and that Charney's estimate of about 3°C for doubled CO (which causes a forcing of 4.3 Watts/m
		Although these forcings are not well-measured, it appears that the net climate forcing is probably much less than the greenhouse forcing.
		Dashed line is the forcing for 1% per year increase of CO Finally, we emphasize that even the best known climate forcing, that due to the greenhouse gases, presents major uncertainties when one attempts to predict the future.
	www.giss.nasa.gov /research/briefs/hansen_05 (789 words)

	Can we defuse the global warming time bomb?
		Insolation and climate changes also affect uptake and release of CO and CH by plants, soil and the ocean, as shown by changes in atmospheric CO and CH that are nearly synchronous with the climate changes (Figure 2).
		Although climate models yield a similar climate sensitivity, the empirical result is more precise and reliable because it includes all the processes operating in the real world, even those we have not yet been smart enough to include in the models.
		Climate forcing by greenhouse gases is now larger than that by the sun, and the greenhouse forcing is increasing monotonically, whereas no significant long-term trend is expected for the sun.
	naturalscience.com /ns/articles/01-16/ns_jeh2.html (2307 words)

	Climate Change 2001: The Scientific Basis
		Note that the patterns of radiative forcing and temperature response are quite different in (a) and (b), but that the patterns of large-scale temperature responses to different forcings are similar in (b) and (c).
		The global mean change in radiative forcing (see Chapter 6) since the pre-industrial period may give an indication of the relative importance of the different external factors influencing climate over the last century.
		To detect the response to anthropogenic or natural climate forcing in observations, we require estimates of the expected space-time pattern of the response.
	www.grida.no /climate/ipcc_tar/wg1/447.htm (866 words)

	Climate and Vegetation Research Group: Courses (GG 101 Spring 2004 Lecture 30)
		Externally-forced climate variations may be due to changes in natural forcing factors, such as solar radiation or volcanic aerosols, or to changes in anthropogenic forcing factors, such as increasing concentrations of greenhouses gases or sulphate aerosols.
		Climate forcing by changes in solar irradiance and volcanism have likely caused fluctuations in global and hemispheric mean temperatures.
		The combination of natural external forcing (solar and volcanic) and internal variability is unlikely to account for the spatio-temporal pattern of change over the past 30-50 years, even allowing for possible amplification of the amplitude of natural responses by unknown feedback processes.
	cybele.bu.edu /courses/gg101spring04/chap06/chap06.html (2473 words)

	RealClimate » What is a first-order climate forcing?
		In it, he has made clear that he feels that apart from greenhouse gases, other climate forcings (the changes that affect the energy balance of the planet) are being neglected in the scientific discussion.
		It is curious to note that this is the combination of forcings that were predominantly used in the simulations discussed in IPCC (1995) where the conclusion was made that the 'balance of evidence' supported the notion of ongoing human-caused climate change.
		Although these climate forcings may not alter the global mean surface temperture, they are first order climate forcings in terms of their substantial role in influencing the climate system including the planetary atmospheric circulation.
	www.realclimate.org /index.php?p=186 (7916 words)

	Dr. James Hansen Statement for the Record
		Climate models have about the same sensitivity, which provides encouraging agreement between the real world and the complex computer models that we use to predict how climate may change in the future.
		The climate forcings are known more precisely for the past 50 years, especially during the past 25 years of satellite measurements.
		C for doubled CO the climate forcing scenario (aerosol changes are very poorly measured), and the simulated heat storage in the ocean (which depends upon the realism of the ocean circulation and mixing).
	www.hq.nasa.gov /office/legaff/hansen5-1.html (5747 words)

	Climate Impact of Quadrupling CO2
		An overview of GFDL climate model results is presented from a series of experiments examining the possible climate impact of a quadrupling of atmospheric CO Much of the recent anthropogenic climate change research has been focused on the issues of climate change detection and projections of climate change over the next century.
		Although the aerosol forcing is highly uncertain and other climate forcings or natural variability may have contributed to the observed changes, the similarity between the modeled and observed global temperature curves suggests that the model's sensitivity is plausible in the light of currently available observations.
		In fact, the anticipated relative future climate forcing contributions from anthropogenic sulfate aerosols and CO are such that the aerosols will become largely irrelevant on the multi-century time scale.
	www.gfdl.gov /~tk/climate_dynamics/climate_impact_webpage.html (2050 words)

	RealClimate » Forcings Forçages
		Forcings in the climate sense are external boundary conditions or inputs to a climate model.
		Almost all of the elements that make up the atmosphere can be considered feedbacks on some timescale, and so defining the forcing is really a function of what feedbacks you allow in the model and for what purpose you are using it.
		A good discussion of recent forcings can be found in Hansen et al (2002) and in Schmidt et al (2004).
	www.realclimate.org /index.php?p=4 (252 words)

	Climate Ark: Climate Change Overview
		A planet's climate is decided by its mass, its distance from the sun and the composition of its atmosphere.
		The projection of future climate change depends partly on the assumptions made about future emissions of greenhouse gases and aerosol precursors and the proportion of emissions remaining in the atmosphere.
		Climate models calculate that the global mean surface temperature could rise by about 1 to 4.5 centigrade by 2100.
	www.climateark.org /overview (713 words)

	Climate change - Wikipedia, the free encyclopedia
		The external factors that can shape climate are often called climate forcings and include such processes as variations in solar radiation, the Earth's orbit, and greenhouse gas concentrations.
		The most important climate processes of the last several million years are the glacial and interglacial cycles of the present ice age.
		In their impact on climate, orbital variations are in some sense an extension of solar variability, because slight variations in the Earth's orbit lead to changes in the distribution and abundance of sunlight reaching the Earth's surface.
	en.wikipedia.org /wiki/Climate_change (2894 words)

	World Climate Report » Climate Forcings
		When the concentration of greenhouse gases is increased numerically, almost all models of climate show an increase in global temperature with the most warming occurring in the Northern Hemisphere’s highest latitudes.
		These results, while confirming that anthropogenic-added climate forcing might have progressively played a dominant role in climate change during the last century, also suggest that the solar impact on climate change during the same period is significantly stronger than what some theoretical models have predicted.
		Recently there have been several papers published that have attempted to use the evolution of the earth’s temperature after big volcanic eruptions as a determinate of the earth’s climate sensitivity—that is, how much the average temperature changes with a change in climate forcing (i.e.
	www.worldclimatereport.com /index.php/category/climate-forcings (1097 words)

	ClimatePrediction.Net gateway (Site not responding. Last check: 2007-10-25)
		Because the climate system is chaotic, tiny changes in things such as temperatures, winds, and humidity in one place can lead to very different paths for the system as a whole.
		The chaotic variability we target in the initial condition ensemble is due to factors internal to the climate system, while things such as solar variability, sulphate (volcanic, etc) forcing and greenhouse gases are treated as external to the climate system.
		The future forcings ensemble is necessary because we don't know what the sun or the volcanoes are going to do over the next fifty years.
	www.climateprediction.net /science/strategy_adv.php (1633 words)

	The Environmental Literacy Council - Climate Change
		Climate itself adjusts from the times of 'ice ages,' when huge ice sheets covered large areas that are currently ice-free, to periods similar to today when ice sheets are largely confined to Antarctica, Greenland, and the floating Arctic sea ice.
		Climate variation occurs as a response to "climate forcings," which are factors that can cause either a warming or cooling of the atmosphere.
		Therefore, when dealing with climate change, scientists need to make a number of assumptions with an ever increasing number of models that focus on different parts of the climate system; all of which makes pinpointing exactly what to expect in terms of future climate change that much more difficult.
	www.enviroliteracy.org /article.php/1146.html (1175 words)

	Climate forcings in the Industrial era -- Hansen et al. 95 (22): 12753 -- Proceedings of the National Academy of ...
		A climate forcing is an imposed perturbation of the Earth's energy balance with space (1).
		Climate forcing by ozone is uncertain because ozone change as a function of altitude is not well measured.
		The principal climate change issue of the past two decades, exemplified by the Charney (41) report, was climate sensitivity.
	www.pnas.org /cgi/content/full/95/22/12753 (3785 words)

	Climate Science: Roger Pielke Sr. Research Group Weblog » Climate Change Forcings and Feedbacks (Site not responding. Last check: 2007-10-25)
		The more heterogeneous climate forcing of land cover/land use change is why NASA reported, based on our peer reviewed research, that “Landcover changes may rival greenhouse gases as cause of climate change“.
		The subject of the importance of the nonlinearity of the climate was also discussed in the Climate Science weblog of December 24 2005.
		The climate changes are large and longlasting because the fuel loadings in modern cities are quite high and the subtropical solar insolation heats the resulting smoke cloud and lofts it into the high stratosphere, where removal mechanisms are slow.
	climatesci.atmos.colostate.edu /?cat=7 (5539 words)

	The Scientific Attitude to Climate Change
		The forcings that drive long-term climate change are not known with an accuracy sufficient to define future climate change.
		The summary implication is a paradigm change (whatever one of those is) for long-term climate projections: uncertainties in climate forcings have supplanted global climate sensitivity as the predominant issue.
		Climate forcing...by tropospheric water vapour, the strongest GHG, is not included...because this water vapour amount is a function of climate and thus represents a feedback, rather than a forcing.
	www.john-daly.com /barrett2.htm (1305 words)

	Data @ NASA GISS: "Efficacy of Climate Forcings" Simulations (Site not responding. Last check: 2007-10-25)
		Maps, graphs and numerical data for many climate diagnostic quantities are provided from the large number of climate simulations that were made for that paper.
		"Fa", the adjusted forcing, is the flux change at the top of the atmosphere (and throughout the stratosphere) after the stratosphere is allowed to adjust radiatively to the presence of the forcing agent.
		"Fs", the fixed SST forcing, is a combination of the flux change at the top of (and throughout) the atmosphere and of the global surface air temperature change after the forcing and with observed sea surface temperature (SST) and sea ice (SI) held fixed.
	data.giss.nasa.gov /efficacy (401 words)

	NOAA Paleoclimatology Global Warming - The Data
		The climate of the Earth is affected by a number of factors.
		The forcings that were probably the most important during the last millennium were: changes in the output of energy from the sun, volcanic eruptions, and changes in the concentration of greenhouse gases in the atmosphere.
		The size of these forcings is expressed in terms of Watts (a flux of energy) per square meter of the Earth's surface.
	www.ncdc.noaa.gov /paleo/globalwarming/gw-forcing.html (299 words)

	[No title]
		Because of the unsteady nature and interactions in the aforementioned climate forcings, significant changes in temperature and precipitation (rain and snow) can occur in Alaska from one month to the next, from season-to-season, from year-to-year and even from one decade to the next.
		Not all climate researchers and oceanographers agree in the existence of or influence that the PDO exerts on the climate of the Pacific Basin.
		In essence, the AO index is a fairly weak measure of the climate forcing in the western Arctic.
	pafc.arh.noaa.gov /climvar/climate-paper.html (7300 words)

	Climate forcings in Goddard Institute for Space Studies SI2000 simulations
		We define the radiative forcings used in climate simulations with the SI2000 version of the Goddard Institute for Space Studies (GISS) global climate model.
		This agreement does not yield an improved assessment of climate sensitivity or a confirmation of the net climate forcing because of possible compensations with opposite changes of these quantities.
		Nevertheless, the results imply that observed global temperature change during the past 50 years is primarily a response to radiative forcings.
	www.agu.org /pubs/crossref/2002/2001JD001143.shtml (548 words)

	Climate Variability and Change. Highlights of Recent Research and Plans for FY 2004 and FY 2005. From our Changing ...
		Climate variability and change can profoundly influence social and natural environments throughout the world, with consequent impacts on natural resources and industry that can be large and far-reaching.
		For example, future changes in climate variability, for example a variation in the frequency and nature of EN SO events or the severity and duration of droughts, will depend partly on changes in global (and regional) mean conditions.
		Climate models project that the high latitude regions are particularly sensitive to climate change because of the positive albedo feedback effects associated with reduction of ice and snow cover, and the reduction of thermal insulation of the ocean that sea ice cover provides, allowing increased heat transfer from the ocean to the atmosphere.
	www.usgcrp.gov /usgcrp/Library/ocp2004-5/ocp2004-5-hi-clivar.htm (5206 words)

	Climate Ark: Temperature and CO2 concentration in the atmosphere since 400,000 years
		Over the last 400,000 years the Earth's climate has been unstable, with very significant temperature changes, going from a warm climate to an ice age in as rapidly as a few decades.
		These rapid changes suggest that climate may be quite sensitive to internal or external climate forcings and feedbacks.
		A possible scenario: anthropogenic emissions of GHGs could bring the climate to a state where it reverts to the highly unstable climate of the pre-ice age period.
	www.climateark.org /overview/02.asp (218 words)

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