Sentences with phrase «estimates of climate sensitivity based»
Here we briefly discuss the radiative forcing estimates used for understanding climate during the last millennium, the mid-Holocene and the Last Glacial Maximum (LGM)(Section 9.3) and in estimates of climate sensitivity based on palaeoclimatic records (Section 9.6.3).
https://www.ipcc.ch/
The relatively slow rate of warming over the past decade has lowered some estimates of climate sensitivity based on surface temperature records.
However, as Hansen notes, empirical estimates of climate sensitivity based on paleoclimate data are consistent with the sensitivity in climate models of approximately 3 °C for doubled atmospheric CO2.
Think about it — if the various estimates of climate sensitivity based on the instrumental period still had such fat tails just five years ago, then why would an extra five years suddenly turn that around and allow calculations of sensitivity based on the instrumental period to now rule out high sensitivities?
«Lewis & Crok perform their own evaluation of climate sensitivity, placing more weight on studies using «observational data» than estimates of climate sensitivity based on climate model analysis.»
While climate contrarians like Richard Lindzen tend to treat the uncertainties associated with clouds and aerosols incorrectly, as we noted in that post, they are correct that these uncertainties preclude a precise estimate of climate sensitivity based solely on recent temperature changes and model simulations of those changes.
Not exact matches
Therefore studies based on observed warming have underestimated climate sensitivity as they did not account for the greater response to aerosol forcing, and multiple lines of evidence are now consistent in showing that climate sensitivity is in fact very unlikely to be at the low end of the range in recent estimates.
The calculations of prospective warming in the OXONIA lecture and the accompanying discussion papers are based on the new climate sensitivity estimates by Murphy et al which were published in Nature, 12 August 2004, vol.
Most of the non-model estimates of climate sensitivity are based on the analyses using other forcings such as solar and aerosols, and the assumption that sensitivity to CO2 will be the same, despite the differences in way these forcings couple to the climate system.
I think that some comment on my energy balance based climate sensitivity estimate of 1.6 - 1.7 °C (details at http://www.webcitation.org/6DNLRIeJH), which underpinned Matt Ridley's WSJ op - ed, would have been relevant and of interest.
A combination of circumstances makes model - based sensitivity estimates of distant times and different climates hard to do, but at least we are getting a good education about it.
But to reiterate: the difference between climate sensitivity estimates based on land vs. ocean data indicates that something is seriously wrong, either with the model, or the data, or some of both.
You may not be able to «prove» such an honest estimate, but it is more likely to be correct than a value based on some estimate of short term climate sensitivity.
The Schmittner et al. analysis marks the insensitive end of the spectrum of climate sensitivity estimates based on LGM data, in large measure because it used a data set and a weighting that may well be biased toward insufficient cooling.
My main criticism of their study is that they have calculated effective climate sensitivity (their ICS) on a basis which is wrong for ICS in GCMs; their basis is also inconsistent with observationally - based estimates of ICS.
There has been an unusual surge of interest in the climate sensitivity based on the last decade's worth of temperature measurements, and a lengthy story in the Economist tries to argue that the climate sensitivity may be lower than previously estimated.
The calculations of prospective warming in the OXONIA lecture and the accompanying discussion papers are based on the new climate sensitivity estimates by Murphy et al which were published in Nature, 12 August 2004, vol.
Therefore studies based on observed warming have underestimated climate sensitivity as they did not account for the greater response to aerosol forcing, and multiple lines of evidence are now consistent in showing that climate sensitivity is in fact very unlikely to be at the low end of the range in recent estimates.
Hegerl et al (2006) for example used comparisons during the pre-industrial of EBM simulations and proxy temperature reconstructions based entirely or partially on tree - ring data to estimate the equilibrium 2xCO2 climate sensitivity, arguing for a substantially lower 5 % -95 % range of 1.5 — 6.2 C than found in several previous studies.
My main criticism of their study is that they have calculated effective climate sensitivity (their ICS) on a basis which is wrong for ICS in GCMs; their basis is also inconsistent with observationally - based estimates of ICS.
Conversely, if «climate sensitivity» for a doubling of CO2 is based on recent measurements and CO rates, and past natural variability is underestimated — as you've shown here — then this implies our estimates of sensitivity per CO2 doubling is too high, not too low.
Could some aspect of our situation, e.g. the extreme rapidity of the forcing change, be sufficiently novel to make Earth's climate respond differently than it has in the past, and could this cause divergence from models based on paleoclimate sensitivity estimates?
IPCC makes all sorts of calculations on the deleterious effects of NOT halting CO2 emissions, based on the same climate sensitivity estimate and a bunch of model «scenarios» on CO2 increase.
Using the IPCC model - based estimate for climate sensitivity and the same logarithmic calculation as for the UK alone, we will have averted 1.2 °C of warming by 2100 by shutting down the world carbon - based economy.
The reports for which you provided links are interesting, but do not provide any empirical evidence in support of the Myhre et al. model - based estimate of CO2 climate sensitivity (clear sky, no feedbacks).
The results of the analysis demonstrate that relative to the reference case, projected atmospheric CO2 concentrations are estimated by 2100 to be reduced by 3.29 to 3.68 part per million by volume (ppmv), global mean temperature is estimated to be reduced by 0.0076 to 0.0184 °C, and sea - level rise is projected to be reduced by approximately 0.074 — 0.166 cm, based on a range of climate sensitivities.
So the two estimates (with and without solar forcing) give me a range of 0.7 C to 1.4 C for the 2xCO2 climate sensitivity, based on actually observed CO2 and temperature records, rather than model simulations and assumptions.
This Nature Climate Change paper concluded, based purely on simulations by the GISS - E2 - R climate model, that estimates of the transient climate response (TCR) and equilibrium climate sensitivity (ECS) based on observations over the historical period (~ 1850 to recent times) were biasClimate Change paper concluded, based purely on simulations by the GISS - E2 - R climate model, that estimates of the transient climate response (TCR) and equilibrium climate sensitivity (ECS) based on observations over the historical period (~ 1850 to recent times) were biasclimate model, that estimates of the transient climate response (TCR) and equilibrium climate sensitivity (ECS) based on observations over the historical period (~ 1850 to recent times) were biasclimate response (TCR) and equilibrium climate sensitivity (ECS) based on observations over the historical period (~ 1850 to recent times) were biasclimate sensitivity (ECS) based on observations over the historical period (~ 1850 to recent times) were biased low.
One of these years the scientiifc community is going to wake up to the fact that there is no sound scientific basis on which anyone can claim that CAGW exists, simply because there is no basis whatsoever on which to base any estimate of climate sensitivity.
These values have been estimated using relatively simple climate models (one low - resolution AOGCM and several EMICs based on the best estimate of 3 °C climate sensitivity) and do not include contributions from melting ice sheets, glaciers and ice caps.
Based on these sensitivities and observed climate trends, we estimate that warming since 1981 has resulted in annual combined losses of these three crops representing roughly 40 Mt or $ 5 billion per year, as of 2002.
[7] Each individual estimate of the SCC is the realization of a Monte Carlo simulation based on a draw from an equilibrium climate sensitivity distribution to model the impact of CO2 emissions on temperature.
another quote from Nic Lewis: Most of the observationally - based estimates of climate sensitivity explicitly adopt a «Bayesian» statistical approach.
The three successive IPCC reports (1991 [2], 1996, and 2001 [3]-RRB- concentrated therefore, in addition to estimates of equilibrium sensitivity, on estimates of climate change over the 21st century, based on several scenarios of CO2 increase over this time interval, and using up to 18 general circulation models (GCMs) in the fourth IPCC Assessment Report (AR4)[4].
These are based on the IPCC model - derived 2xCO2 climate sensitivity of 3.2 °C, so let's stick with that estimate for now.
On this basis we can estimate the 2xCO2 climate sensitivity, based on IPCC's ice core estimated of pre-industrial CO2 levels and current Mauna Loa CO2 measurements plus the 161 - year HadCRUT surface temperature record.
«A particularly robust way of empirically estimating climate sensitivity is the so - called «energy - budget» method, which is based on a fundamental physical law — the conservation of energy.
Based on the principles of radiative physics and reasonable estimates of feedbacks and climate sensitivity, I would say that any current oscillations beyond those we already know can't be strong so strong that they leave little or no room for what anthropogenic emissions are contributing to the temperature trend.
Stating the «IPCC position on climate sensitivity is largely based on GCMs» (Montford) is different from «argu [ing] that GCMs are crucial to estimating climate sensitivity (your interpretation of Monford).»
Indeed, there are examples in IPCC reports of willingness to acknowledge the importance of expert (subjective) judgment, if on a limited basis (e.g., see discussions of climate sensitivity, detection and attribution and climate and weather extremes in WGI report, assessment of response strategies in the WGII report of AR4; see also Knutti and Hegerl (2008) for futher details on the role of expert judgement in estimating climate sensitivity).
«uncertainty» (in the IPCC attribution of natural versus human - induced climate changes, IPCC's model - based climate sensitivity estimates and the resulting IPCC projections of future climate) is arguably the defining issue in climate science today.
To add to the point made by Chris Colose, the low sensitivity estimates from Lindzen or Spencer / Braswell that he refers to are based on short term climate fluctuations of the ENSO type.
When Armour factored rising sensitivity into that 2013 observation - based Nature Geoscience report and recalculated climate sensitivity, he got a best estimate of 2.9 º C — a value well within the IPCC's consensus range and the range predicted by models.
The probability distributions give a most likely estimate of 3 °C of warming for a doubling of CO2, and all pragmatic scientists tend to work on the basis that the climate sensitivity is not drastically more than that.
The answer will tell us a lot about the validity of the model - based estimate for climate sensitivity used by IPCC (based on an «argument from ignorance», as has been pointed out)..
But it still makes the basic «argument from ignorance» that most of the past warming can be attributed to anthropogenic factors, i.e. by human CO2, in supporting itsmodel - based 2xCO2 climate sensitivity estimate.
[Lorius et al., 1990] concluded from their analysis that climate sensitivity to a doubling of CO2 is 3 - 4ºC, in good agreement with independent estimates based on the physical understanding of CO2 forcing and relevant feedbacks as coded in models.
The accessibility of deep ocean heat to the climate system tells us that the equilibration time relevant to multidecadal climate sensitivity estimates is longer than an interval based on upper ocean measurements, and so sensitivity will be underestimated if only the shorter interval is used.
In reply to Joel Shore, an earlier commenter had asked me to outline how Professor Lindzen reached a quantitative conclusion, and I replied by providing the quantitative basis and pointing out that application of the value he assigns to lambda seems in line with the IPCC's interval of climate - sensitivity estimates.
Although there has been a slower rate of atmospheric warming during the past 18 years, this does not undermine the fundamental physics of global warming, the scientific basis of climate models or the estimates of climate sensitivity.