radiative forcing a change in average net radiation at the top of the troposphere resulting from a change in either solar or infrared radiation due to a change in atmospheric greenhouse gases concentrations; perturbance in the balance between incoming solar radiation and outgoing infrared radiation
Radiative Forcing A change in average net radiation (in W m - 2) at the top of the troposphere resulting from a change in either solar or infrared radiation due to a change in atmospheric greenhouse gases concentrations; perturbance in the balance between incoming solar radiation and outgoing infrared radiation.
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.
Climate model projections neglecting these
changes would continue to overestimate the
radiative forcing and global warming
in coming decades if these aerosols remain present at current values or increase.
«What is most interesting is that there are big shifts
in the surface mass balance that occur from only very small
changes in radiative forcing,» said Ullman, who is
in OSU's College of Earth, Ocean, and Atmospheric Sciences.
As we explain
in our glossary item, climatologists use the concept of
radiative forcing and climate sensitivity because it provides a very robust predictive tool for knowing what model results will be, given a
change of
forcing.
This
change in radiative forcing is described as «idealized» by the CMIP group [2].
That is, a
change in radiative forcing of about 4 W / m2 would give around 1 °C warming.
Dynamical effects (
changes in the winds and ocean circulation) can have just as large an impact, locally as the
radiative forcing from greenhouse gases.
While a relatively minor part of the overall aerosol mass,
changes in the anthropogenic portion of aerosols since 1750 have resulted
in a globally averaged net
radiative forcing of roughly -1.2 W / m2,
in comparison to the overall average CO2
forcing of +1.66 W / m2.
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.
[Response: A similar conclusion to the one cited by Gavin above was reached independently by a panel of scientists (of which I was a member) convened to report on these issues by the National Academy of Sciences last year, resulting
in the NAS report «
Radiative Forcing of Climate
Change: Expanding the Concept and Addressing Uncertainties (2005)».
Forcing caused by changes in the Sun's brightness, by dust in the atmosphere, or by volcanic aerosols can also be translated into radiative f
Forcing caused by
changes in the Sun's brightness, by dust
in the atmosphere, or by volcanic aerosols can also be translated into
radiative forcingforcing.
Suppose also that — DESPITE THIS STABILIZING MECHANISM some as - yet unknown ocean circulation cycle operates that is the sole cause of the Holocene centennial scale fluctuations, and that this cycle has reversed and is operating today, yielding a temperature
change that happens to mimic what models give
in response to
radiative forcing changes.
Changes in TSI can be converted into a
radiative forcing, which tells us the energy imbalance it causes on Earth.
«
In today's atmosphere, the radiative forcing from human activities is much more important for current and future climate change than the estimated radiative forcing from changes in natural processes.&raqu
In today's atmosphere, the
radiative forcing from human activities is much more important for current and future climate
change than the estimated
radiative forcing from
changes in natural processes.&raqu
in natural processes.»
Where «dT» is the
change in the Earth's average surface temperature, «λ» is the climate sensitivity, usually with units
in Kelvin or degrees Celsius per Watts per square meter (°C / [W - m - 2]-RRB-, and «dF» is the
radiative forcing.
This is a very straightforward and easy to understand formula - the larger the
change in solar irradiance, the larger the energy imbalance it causes, and thus the larger the
radiative forcing.
If you doubled CO2 and let the system come into equilibrium, the imbalance you'd measure from space would be zero — but there would still be about 4 W / m ** 2 of
radiative forcing from the
change in CO2.
In addition, researchers calculated the changes in the shortwave and longwave and net radiation between the pre-industrial simulation and the present - day simulations to estimate the radiative forcing resulting from the aerosol effects on cirrus cloud
In addition, researchers calculated the
changes in the shortwave and longwave and net radiation between the pre-industrial simulation and the present - day simulations to estimate the radiative forcing resulting from the aerosol effects on cirrus cloud
in the shortwave and longwave and net radiation between the pre-industrial simulation and the present - day simulations to estimate the
radiative forcing resulting from the aerosol effects on cirrus clouds.
He then uses what information is available to quantify (
in Watts per square meter) what
radiative terms drive that temperature
change (for the LGM this is primarily increased surface albedo from more ice / snow cover, and also
changes in greenhouse gases... the former is treated as a
forcing, not a feedback; also, the orbital variations which technically drive the process are rather small
in the global mean).
Where «dT» is the
change in the Earth's average surface temperature, «λ» is the climate sensitivity, usually with units
in Kelvin or degrees Celsius per Watts per square meter (°C / [W m - 2]-RRB-, and «dF» is the
radiative forcing, which is discussed
in further detail
in the Advanced rebuttal to the «CO2 effect is weak» argument.
The top priorities should be reducing uncertainties
in climate sensitivity, getting a better understanding of the effect of climate
change on atmospheric circulation (critical for understanding of regional climate
change,
changes in extremes) and reducing uncertainties
in radiative forcing — particularly those associated with aerosols.
Similarly, many studies that attempt to examine the co-variability between Earth's energy budget and temperature (such as
in many of the pieces here at RC concerning the Spencer and Lindzen literature) are only as good as the assumptions made about base state of the atmosphere relative to which
changes are measured, the «
forcing» that is supposedly driving the
changes (which are often just things like ENSO, and are irrelevant to
radiative - induced
changes that will be important for the future), and are limited by short and discontinuous data records.
The surface temperature
change is proportional to the sensitivity and
radiative forcing (
in W m - 2), regardless of the source of the energy imbalance.
However,
in view of the fact that cloud feedbacks are the dominant contribution to uncertainty
in climate sensitivity, the fact that the energy balance model used by Schmittner et al can not compute
changes in cloud
radiative forcing is particularly serious.
«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.
You are arguing that 100ppm
change in radiative forcing for CO2, amounting to 0.6 deg C
change, multiplied by a wv feedback giving 1.8 deg C
change, plays an important part
in raising the sea level by 100 meters.
Jo's scientific interests include
radiative transfer
in the atmosphere, climate modelling,
radiative forcing of climate
change and the influence of solar irradiance variability on climate.
Abstract:» The sensitivity of global climate with respect to
forcing is generally described
in terms of the global climate feedback — the global
radiative response per degree of global annual mean surface temperature
change.
The researchers discovered that periods of increased
radiative forcing could produce drought - like conditions that extended indefinitely and that these conditions were closely tied to prolonged
changes in Pacific Ocean surface temperatures.
Some other
forcings have a very small global
radiative forcing and yet lead to large impacts (orbital
changes for instance) through components of the climate that aren't included
in the default set - up.
Maybe it was due to
changes in CO2
radiative forcing (
in part) since historical CO2 levels weren't as stable as assumed by the IPCC, at least that's what van Hoof et al. conclude from CO2 data derived from stomatal frequency analysis.
Your earlier # 182 was equally disconcerting where you quoted Norris and Slingo (2009) saying «At present, it is not known whether
changes in cloudiness will exacerbate, mitigate, or have little effect on the increasing global surface temperature caused by anthropogenic greenhouse
radiative forcing.»
It's a theory now substantiated by physics and observations regarding total
radiative forcing and sensitivity, and
in our current case of warming attributable to increased
forcing agents form human / industrial means we are experiencing a
change in trends pertaining to weather events driven by total
change factors.
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.
While the local, seasonal climate
forcing by the Milankovitch cycles is large (of the order 30 W / m2), the net
forcing provided by Milankovitch is close to zero
in the global mean, requiring other
radiative terms (like albedo or greenhouse gas anomalies) to
force global - mean temperature
change.
And yet, Simon, you were responding to a set of comments which were about climate sensitivity, for which
radiative forcing would be a much more relevant metric — and you responded
in a fashion which gave no suggestion that you were
changing the topic.
On the possibility of a
changing cloud cover «
forcing» global warming
in recent times (assuming we can just ignore the CO2 physics and current literature on feedbacks, since I don't see a contradiction between an internal
radiative forcing and positive feedbacks), one would have to explain a few things, like why the diurnal temperature gradient would decrease with a planet being warmed by decreased albedo... why the stratosphere should cool... why winters should warm faster than summers... essentially the same questions that come with the cosmic ray hypothesis.
Changes in the planetary and tropical TOA radiative fluxes are consistent with independent global ocean heat - storage data, and are expected to be dominated by changes in cloud radiative f
Changes in the planetary and tropical TOA
radiative fluxes are consistent with independent global ocean heat - storage data, and are expected to be dominated by
changes in cloud radiative f
changes in cloud
radiative forcing.
As an example of the possible extreme
change in radiative forcing in a 50 - year time horizon for Isaken et al (2011)'s 4 x CH4 (i.e. quadrupling the current atmospheric methane burden) case of additional emission of 0.80 GtCH4 / yr is 2.2 Wm - 2, and as the
radiative forcing for the current methane emissions of 0.54 GtCH4 / yr is 0.48 Wm - 2, this give an updated GWP for methane, assuming the occurrence of Isaksen et al's 4 x CH4 case
in 2040, would be: 33 (per Shindell et al 2009, note that AR5 gives a value of 34) times (2.2 / [0.8 + 0.48]-RRB- divided by (0.54 / 0.48) = 50.
In fact, these past climate changes allow us to learn how sensitive the earth's climate system is to the known radiative forcing that we are producing by increasing the levels of greenhouse gases in the atmospher
In fact, these past climate
changes allow us to learn how sensitive the earth's climate system is to the known
radiative forcing that we are producing by increasing the levels of greenhouse gases
in the atmospher
in the atmosphere.
Gerald Marsh offered this opinion
in «A Global Warming Primer» (page 4 - excerpt) «
Radiative forcing is defined as the change in net downward radiative flux at the tropopause resulting from any process that acts as an external agent to the climate system; it is generally measured i
Radiative forcing is defined as the
change in net downward
radiative flux at the tropopause resulting from any process that acts as an external agent to the climate system; it is generally measured i
radiative flux at the tropopause resulting from any process that acts as an external agent to the climate system; it is generally measured
in W / m2.
Consequently, as they say slightly earlier
in the abstract: «At present, it is not known whether
changes in cloudiness will exacerbate, mitigate, or have little effect on the increasing global surface temperature caused by anthropogenic greenhouse
radiative forcing.»
Mike's work, like that of previous award winners, is diverse, and includes pioneering and highly cited work
in time series analysis (an elegant use of Thomson's multitaper spectral analysis approach to detect spatiotemporal oscillations
in the climate record and methods for smoothing temporal data), decadal climate variability (the term «Atlantic Multidecadal Oscillation» or «AMO» was coined by Mike
in an interview with Science's Richard Kerr about a paper he had published with Tom Delworth of GFDL showing evidence
in both climate model simulations and observational data for a 50 - 70 year oscillation
in the climate system; significantly Mike also published work with Kerry Emanuel
in 2006 showing that the AMO concept has been overstated as regards its role
in 20th century tropical Atlantic SST
changes, a finding recently reaffirmed by a study published
in Nature),
in showing how
changes in radiative forcing from volcanoes can affect ENSO,
in examining the role of solar variations
in explaining the pattern of the Medieval Climate Anomaly and Little Ice Age, the relationship between the climate
changes of past centuries and phenomena such as Atlantic tropical cyclones and global sea level, and even a bit of work
in atmospheric chemistry (an analysis of beryllium - 7 measurements).
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 forcin
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 forcin
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 forcin
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 forcin
in large part, reflect the
forced response of ENSO to past volcanic and solar
radiative forcing.
Abstract:» The sensitivity of global climate with respect to
forcing is generally described
in terms of the global climate feedback — the global
radiative response per degree of global annual mean surface temperature
change.
Given the economic tenor of many news stories, an analogy to inflation may be useful
in clarifying the idea of slow but steady
radiative bracket creep, as the CO2
forcing can be outlined
in terms of its effect on the
radiative balance, which reduces to watts / M2 and their rate of
change.
But models based on physical principles also reproduce the response to seasonal and spatial
changes in radiative forcing fairly well, which is one of the many lines of evidence that supports their use
in their prediction of the response to anthropogenic
forcing.
It is not,
in principle, impossible for coupled ocean - atmosphere climate to be chaotic, but all evidence so far points to the likelihood that the strength of the response to GHG
radiative forcing changes overwhelms the effect of any chaos there may be
in the system.