Sentences with phrase «radiative forcing over»

These differences can be quantified by comparing the range of shortwave and longwave forcings across the multi-model ensemble against standard estimates of radiative forcing over the historical record.

«As it happens, he is claiming AGW is a smaller contributing factor because the difference in his calculation sprind insolation (on a particular day) over a 1000 years is greater than the radiative forcing over the last 250 years.»

The theory is that climate will warm in proportion to changes in radiative forcing over time (+ equilibrium «pipeline» warming).

Ice albedo feedback change is mainly limited to high latitude NH * land * during deglaciation, and its effects — though strong — are limited compared to those of a radiative forcing over the global ocean.

Overall, they find that by far the largest radiative forcing over the past 250 years comes from the increased greenhouse effect, which we also know is due to human fossil fuel combustion (Figure 3).

«Quantifying the role of solar radiative forcing over the 20th century -LSB-...] However, we also find that the largest contribution to the 20th century warming comes from anthropogenic sources.»

I was interested to read in the IPCC reports that radiative forcing over the polar regions is less than radiative forcing elsewhere.

The report not only compared the changes in radiative forcing over the last 20 years, it also highlighted the quantities of greenhouse gases in the atmosphere.

http://www.springerlink.com/content/lm0024kv72t3841w/ «The simulated magnitude of hydrological changes over land are much larger when compared to changes over oceans in the recent marine cloud albedo enhancement study since the radiative forcing over land needed (− 8.2 W m − 2) to counter global mean radiative forcing from a doubling of CO2 (3.3 W m − 2) is approximately twice the forcing needed over the oceans (− 4.2 W m − 2).

The spatial distribution of the forcings is similar in the studies showing strongest radiative forcings over industrial regions of the Northern Hemisphere although the ratio of the annual mean Northern Hemisphere / Southern Hemisphere radiative forcing varies from 2.0 (Graf et al., 1997) to 6.9 (Myhre et al., 1998c)(see Section 6.14.2 for further details).

Not exact matches

China's stated aim of improving air quality over the coming years would change this radiative forcing, leading to a rather counter-intuitive consequence; the increase in China's contribution to global warming.

Near - global satellite aerosol data imply a negative radiative forcing due to stratospheric aerosol changes over this period of about — 0.1 W / m2, reducing the recent global warming that would otherwise have occurred.

Pierre, could you comment on what, exactly, is new in the recent Philipona paper, compared with the two similar papers they published last year («Greenhouse forcing outweighs decreasing solar radiation driving rapid temperature rise over land», «Radiative forcing — measured at Earth's surface — corroborate the increasing greenhouse effect»)?

We can estimate this independently using the changes in ocean heat content over the last decade or so (roughly equal to the current radiative imbalance) of ~ 0.7 W / m2, implying that this «unrealised» forcing will lead to another 0.7 × 0.75 ºC — i.e. 0.5 ºC.

«They're pretty evenly distributed across the atmosphere,» said Stephen Montzka, a NOAA scientist who monitors global changes in HFCs and studies their radiative forcing effects over time.

I also note that if Asia (particularly China) converts its many existing coal - fired power plants to methane (from hydrofracking) over the next few decades, then the air pollution in this part of the world will likely be reduced, which would further increase radiative forcing on the Earth.

The model results (which are based on driving various climate models with estimated solar, volcanic, and anthropogenic radiative forcing changes over this timeframe) are, by in large, remarkably consistent with the reconstructions, taking into account the statistical uncertainties.

A lot of the remaining variability you see averages out over the annual cycle, and as I said, if you just take the part that actually correlates with PDO and SOI, you'd get an even smaller radiative forcing coefficient.

In fact, there is reasonably compelling evidence that changes in drought in the western U.S. over the past millennium may, in large part, reflect the forced response of ENSO to past volcanic and solar radiative forcing.

This mostly reflects the response to global radiative forcings, which are dominated by anthropogenic forcing over the 20th Century.

Given those assumptions, looking at the forcing over a long - enough multi-decadal period and seeing the temperature response gives an estimate of the transient climate response (TCR) and, additionally if an estimate of the ocean heat content change is incorporated (which is a measure of the unrealised radiative imbalance), the ECS can be estimated too.

So for example deglaciation warmed global mean temps by about 5 C over 10k years with a radiative forcing of about 6.5 W / m2 (total of both GHG increases and albedo decreases).

[Response: To pre-empt some mutual incomprehension, note that industrial CO2 rises are certainly an anthropgenic forcing and not a response (see here and here), but clearly CO2 changes over glacial - interglacial cycles is both a response (to Milankovitch - driven changes) and a forcing (since the additional radiative forcing from CO2 is about a third of that needed to keep the ice ages as cold as they are — see here).

In this way, the response of LW fluxes (PR) and convection (CR) tend to spread the temperature response vertically from where forcings occur — not generally eliminating the effect of RF distribution over height, although in the case with convection driven by differential radiative heating within a layer, CR can to a first approximation evenly distribute a temperature response over such a layer.

The effect of band widenning is a reduction in net upward LW flux (this is called the radiative forcing), which is proportional to a change in area under the curve (a graph of flux over the spectrum); the contribution from band widenning is equal to the amount by which the band widens (in units ν) multiplied by - Fνup (CO2).

The variation of RF over a layer, increasing / decreasing with height, means that there is a forced convergence / divergence of radiative fluxes; the RF acting on a layer is equal to the difference between RF at the top and bottom of the layer and is positive / negative if the RF is greater / smaller at the top.

It presents a significant reinterpretation of the region's recent climate change origins, showing that atmospheric conditions have changed substantially over the last century, that these changes are not likely related to historical anthropogenic and natural radiative forcing, and that dynamical mechanisms of interannual and multidecadal temperature variability can also apply to observed century - long trends.

Under most scenarios of late 20th century and future anthropogenic radiative forcing, a steady, rather than accelerating, rise in global and hemispheric mean temperature is predicted over timescales of decades.

See Stowasser & Hamilton, Relationship between Shortwave Cloud Radiative Forcing and Local Meteorological Variables Compared in Observations and Several Global Climate Models, Journal of Climate 2006; Lauer et al., The Impact of Global Warming on Marine Boundary Layer Clouds over the Eastern Pacific — A Regional Model Study, Journal of Climate 2010.

The results «indicate that a weak radiative forcing by carbon dioxide is highly unlikely» and that a «climate sensitivity greater than 1.5 °C has probably been a robust feature of the Earth's climate system over the past 420 million years»

The climate sensitivity is defined as the equilibrated change in global mean surface air temperature (SAT) for a given change in radiative forcing and has been a major focus of climate research over the last three decades.

Natural radiative forcing (solar + volcanic) actually leads to a net cooling over the 20th century, and the remaining (internal) natural variability could not possibly account for the late 20th century warming.

Total radiative forcing (W m − 2) of the GCAM reference and RCP4.5 scenarios over the model simulation period

The relative proportion of the non-CO2 components of positive radiative forcing remains constant over time.

Even though some of the CMIP models produce a lot of global warming, all of them are still stable in this regard, with net increases in lost radiation with warming (NOTE: If analyzing the transient CMIP runs where CO2 is increased over long periods of time, one must first remove that radiative forcing in order to see the increase in radiative loss).

The unrealized warming has been fairly constant over the past ~ 50 years whereas the radiative forcing increases the further back in time you choose your initial point.

The current role of methane looms large, he says, contributing over 40 percent of current radiative forcing from all greenhouse gases, based on the latest science from the Intergovernmental Panel on Climate Change.

Therefore, our results confirm that positive radiative forcings (e.g., from human - caused increases in greenhouse gas concentrations) are necessary in order for the Earth to have warmed as much as it did over the 20th century.

The albedo change resulting from the snowline retreat on land is similarly large as the retreat of sea ice, so the combined impact could be well over 2 W / sq m. To put this in context, albedo changes in the Arctic alone could more than double the net radiative forcing resulting from the emissions caused by all people of the world, estimated by the IPCC to be 1.6 W / sq m in 2007 and 2.29 W / sq m in 2013.»

The decadal changes in TOA flux associated with ENSO and the PDO suggest that the longer term patterns associated with changing SST over centuries to millennia are associated with significant but unknowable changes in cloud radiative forcing.

Fortunately, the negative and positive forcings are roughly equal and cancel each other out, and the natural forcings over the past half century have also been approximately zero (Meehl 2004), so the radiative forcing from CO2 alone gives us a good estimate as to how much we expect to see the Earth's surface temperature change.

In addition, the term pathway is meant to emphasize that it is not only a specific long - term concentration or radiative forcing outcome, such as a stabilization level, that is of interest, but also the trajectory that is taken over time to reach that outcome.

This unique feature of the Antarctic atmosphere has been shown to result in a negative greenhouse effect and a negative instantaneous radiative forcing at the top of the atmosphere (RFTOA: INST), when carbon dioxide (CO2) concentrations are increased, and it has been suggested that this effect might play some role in te recent cooling trends observed over East Antarctica.

Radiative forcing from methane makes up over 15 % of the recorded change with 60 % of methane production coming from human activities.

As a consequence, like the RFTP: INST, the stratosphere - adjusted radiative forcing at the TOA is positive over all of Antarctica and, in the model presented herein, surface temperatures increase everywhere over that continent in response to quadrupled CO2.

Here we show that accounting for recent cooling in the eastern equatorial Pacific reconciles climate simulations and observations.We present a novel method of uncovering mechanisms for global temperature change by prescribing, in addition to radiative forcing, the observed history of sea surface temperature over the central to eastern tropical Pacific in a climate model.

My understanding is that the issue over the theory of CO2 forcing is not disagreement over radiative energy transport but 1) The additional forcing required to make radiative forcing a potential crisis and 2) the lack of consideration of convective heat transfer.

Scientists have predicted that GHG forcing resulting from the physics of radiative transfer will cause energetic imbalance for over a century.

So the 3.7 W m - 2 calculation for global radiative forcing could be refined perhaps by an improved experimental design (not necessarily by improved radiative transfer models) running RT models at each grid cell over the globe, over the diurnal cycle and the annual cycle for say 30 years, for the two different CO2 concentrations, such a detailed calculation would refine the 3.7 value.

Equivalent carbon dioxide (CO2) emission - The amount of carbon dioxide emission that would cause the same integrated radiative forcing, over a given time horizon, as an emitted amount of a well mixed heat - trapping gas (greenhouse gas) or a mixture of well mixed greenhouse gases.