Thermocline flux exchange during the Pinatubo event

Douglass, D. H.; Knox, Robert; Pearson, Benjamin D.; Clark, Alfred

doi:10.1029/2006gl026355

Cited by 12 publications

(12 citation statements)

References 19 publications

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“…We resist the temptation to assess climate feedback immediately after the four major eruptions since 1900 because our framework is based upon stratospherically adjusted RF, and relating the ERBE measurements (top of atmosphere) to the tropopause is beyond the scope of this study. If the true influence of Pinatubo on global cooling is as small as suggested by our lower limits, and there was indeed a strong, global, negative RF anomaly at the tropopause, then perhaps there was a negative feedback following the eruption of Pinatubo, as suggested by Douglass and Knox (2005) and Douglass et al (2006). Stenchikov et al (2009) state; "In this study, Pinatubo aerosols globally decrease the incoming net radiative flux at the top of the atmosphere by about 3 W m −2 at maximum that is consistent with most of the IPCC-AR4 models .…”

Section: T Canty Et Al: a Critical Evaluation Of Volcanic Coolingmentioning

confidence: 86%

“…Douglass and Knox (2005) conducted a regression analysis of MSU lower tropospheric temperature measurements and concluded the atmosphere exhibited a negative feedback following the eruption of Pinatubo. This paper has been discussed in a series of published comments and replies following initial publication, concluding with another paper, Douglass et al (2006), that reinforces their notion of a negative feedback within the climate system in the short time period following the Pinatubo eruption. Our estimates of climate feedback, given above, represent a best fit to the entire 111 yr temperature record, without direct focus on the time period immediately following major eruptions.…”

Section: T Canty Et Al: a Critical Evaluation Of Volcanic Coolingmentioning

confidence: 93%

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An empirical model of global climate – Part 1: A critical evaluation of volcanic cooling

et al. 2013

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Abstract. Observed reductions in Earth's surface temperature following explosive volcanic eruptions have been used as a proxy for geoengineering of climate by the artificial enhancement of stratospheric sulfate. Earth cools following major eruptions due to an increase in the reflection of sunlight caused by a dramatic enhancement of the stratospheric sulfate aerosol burden. Significant global cooling has been observed following the four major eruptions since 1900: Santa María, Mount Agung, El Chichón and Mt. Pinatubo, leading IPCC (2007) to state "major volcanic eruptions can, thus, cause a drop in global mean surface temperature of about half a degree Celsius that can last for months and even years". We use a multiple linear regression model applied to the global surface temperature anomaly to suggest that exchange of heat between the atmosphere and ocean, driven by variations in the strength of the Atlantic Meridional Overturning Circulation (AMOC), has been a factor in the decline of global temperature following these eruptions. The veracity of this suggestion depends on whether sea surface temperature (SST) in the North Atlantic, sometimes called the Atlantic Multidecadal Oscillation, but here referred to as Atlantic Multidecadal Variability (AMV), truly represents a proxy for the strength of the AMOC. Also, precise quantification of global cooling due to volcanoes depends on how the AMV index is detrended. If the AMV index is detrended using anthropogenic radiative forcing of climate, we find that surface cooling attributed to Mt. Pinatubo, using the Hadley Centre/University of East Anglia surface temperature record, maximises at 0.14 °C globally and 0.32 °C over land. These values are about a factor of 2 less than found when the AMV index is neglected in the model and quite a bit lower than the canonical 0.5 °C cooling usually attributed to Pinatubo. This result is driven by the high amplitude, low frequency component of the AMV index, demonstrating that reduced impact of volcanic cooling upon consideration of the AMV index is driven by variations in North Atlantic SST that occur over time periods much longer than those commonly associated with major volcanic eruptions. The satellite record of atmospheric temperature from 1978 to present and other century-long surface temperature records are also consistent with the suggestion that volcanic cooling may have been over estimated by about a factor of 2 due to prior neglect of ocean circulation. Our study suggests a recalibration may be needed for the proper use of Mt. Pinatubo as a proxy for geoengineering of climate. Finally, we highlight possible shortcomings in simulations of volcanic cooling by general circulation models, which are also being used to assess the impact of geoengineering of climate via stratospheric sulfate injection.

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Section: T Canty Et Al: a Critical Evaluation Of Volcanic Coolingmentioning

confidence: 86%

Section: T Canty Et Al: a Critical Evaluation Of Volcanic Coolingmentioning

confidence: 93%

An empirical model of global climate – Part 1: A critical evaluation of volcanic cooling

et al. 2013

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“…This effect should, if correct, provide a powerful negative feedback. As mentioned earlier, ocean delay is itself proportional to climate sensitivity, and the work of Lindzen and Giannitsis (1998) and Douglass et al, (2006) strongly suggested that the observed delay time is too short to allow large sensitivities.…”

Section: "The Size Of the Recently Observed Global Warming Over A Fementioning

confidence: 99%

Taking Greenhouse Warming Seriously

Lindzen

2007

Energy & Environment

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INTRODUCTIONIn science, there is an art to simplifying complex problems so that they can be meaningfully analyzed. If one oversimplifies, the analysis is meaningless. If one doesn't simplify, then one often cannot proceed with the analysis. When it comes to global warming due to the greenhouse effect, it is clear that many approaches are highly oversimplified. This includes the simple 'blanket' picture of the greenhouse effect shown in Figure 1. We will approach the issue more seriously in order to see whether one can reach reasonably rigorous conclusions. It turns out that one can.In Section 2, we present a physically correct view of the greenhouse effect, and show how this view enables us to use modeling results and observations in order to estimate a bound on the greenhouse contribution to recent surface warming of about 1/3. This is, indeed, somewhat less than the iconic claim in the IPCC Summary for Policymakers of Working Group 1 which claimed that it was likely that most of the recent warming was due to man. The present estimate is more constrained, and thereby suggests a lower climate sensitivity than is commonly found in current models. Section 3 discusses the origin of the contradicted claim as well as its relation to claims of high climate sensitivity. It turns out that far more than the iconic claim is needed for the sensitivity required for alarm. The main point of this paper is simply to illustrate why serious and persistent doubts remain concerning the danger of anthropogenic global warming despite the frequent claims that 'the science is settled.'

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“…Many estimates based on those methods have therefore been criticized; we generally have low confidence in relying on them in this assessment, but provide further references to studies and critical comments here for completeness 7,24,56,93,225,231,259,269, . Similarly, the response to volcanic eruptions provides a test for models 302 but in our view the implications for ECS are unclear since the timescale and type of forcing is very different, the feedbacks arising are different, and the response is difficult to separate from El Niño variability 185,[303][304][305][306][307][308][309][310][311] . It has also been attempted to estimate TCR from the observed temperature response to the sunspot cycle 312 .…”

Section: Constraints From the Observed Transient Warmingmentioning

confidence: 99%

Beyond equilibrium climate sensitivity

2017

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Equilibrium climate sensitivity characterizes the Earth' long-term global temperature response to an increased atmospheric carbon dioxide concentration. It has reached almost iconic status as the single number that describes how severe climate change will be. The consensus 'likely' range for climate sensitivity of 1.5-4.5 o C today is the same as given by Jule Charney in 1979, but is now based on quantitative evidence from across the climate system, and through climate history. The quest to constrain climate sensitivity has revealed important insights into the timescales of the climate system response, natural variability, limitations in observations and climate models, but also concerns about the simple concepts underlying climate sensitivity and radiative forcing, which open avenues to better understand and constrain the climate response to forcing. Estimates of the transient climate response are better constrained by observed warming and are more relevant for predicting warming over the next decades. Newer metrics relating global warming directly to the total emitted CO2 show that in order to keep warming to within 2 o C, future CO2 emissions have to remain strongly limited, irrespective of climate sensitivity being at the high or low end.If we increase the amount of CO2 in the Earth's atmosphere and wait for climate to respond, how much warmer would surface temperatures eventually get? What seems like a simple but important question to ask given current and projected human-induced CO2 emissions, is an issue that scientists have struggled with since the first rough estimates were made more than a century ago 1,2 . To answer that question, starting in the 1960s, scientists have used energy balance arguments combined with observed changes in the global energy budget, evaluated comprehensive climate models against observations, and analyzed the relationship between external forcing and climate change over different climate states in the past (see Methods for a list of early publications). The idea of using those different lines of evidence has not changed, but progress in simulating climate, a longer and more accurate observed record of past warming, and better constrained paleoclimate reconstructions now offer more possibilities to evaluate and constrain models. However, recent research has pointed out previously unknown limitations in some of the concepts and assumptions underlying a single constant climate sensitivity 3 . While publications have appeared using various methods, arguably the most important conceptual recent insights is that feedbacks change with equilibration time, an insight that is based on studies in comprehensive climate models. Other recent insights show that the treatment of observations is important 4 . Knowing, to first order, how the global climate will warm in response to increased CO2 is critical: for unabated emissions, it is the difference between a hot and an extremely hot future. The value of halving the uncertainty in that projection may be in the trillions of dollars 5 . Here w...

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Thermocline flux exchange during the Pinatubo event

Cited by 12 publications

References 19 publications

An empirical model of global climate – Part 1: A critical evaluation of volcanic cooling

An empirical model of global climate – Part 1: A critical evaluation of volcanic cooling

Taking Greenhouse Warming Seriously

Beyond equilibrium climate sensitivity

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