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<div class="ms-outlook-mobile-reference-message skipProofing"><font color="#000000" face="Arial">Please join us for a Meteorology seminar on Tuesday April 21 at 3 PM, given by Prof. Ming Cai (FSU). He will speak about "<i>Climate sensitivity emerges from first-principles
temperature feedback circuits”</i> (abstract below).</font></div>
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<font face="Arial"><span style="background-color: rgb(255, 255, 255);"><font color="#000000">Prof.
<span style="caret-color: rgb(0, 0, 0);">Cai will present his seminar in person in 1044, but a</span> Zoom link is available for those with a medical excuse or approved work off-campus. Please contact Allison Wing (</font></span><span style="color: rgb(0, 134, 240);"><a href="mailto:awing@fsu.edu" class="ms-outlook-linkify" title="mailto:awing@fsu.edu" data-ogsc="rgb(0, 134, 240)" data-outlook-id="3b775de3-847f-4320-b67e-8836571d6069" style="color: rgb(0, 134, 240);">awing@fsu.edu</a></span><span style="color: rgb(0, 0, 0); background-color: rgb(255, 255, 255);">)
for the link.</span></font></div>
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<font face="Arial">DATE: Tuesday April 21</font></div>
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<font face="Arial">TIME: 3-4 PM, please join early for refreshments</font></div>
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<font face="Arial">LOCATION: EOA 1044 </font></div>
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<font face="Arial">SPEAKER: Prof. Ming Cai</font></div>
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<div style="color: rgb(0, 0, 0);"><font face="Arial">We look forward to seeing you there!</font></div>
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<div style="direction: ltr; color: rgb(0, 0, 0);"><font face="Arial">=========</font></div>
<div style="direction: ltr; color: rgb(0, 0, 0);"><font face="Arial">Title: <i>Climate sensitivity emerges from first-principles temperature feedback circuits</i></font></div>
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<div style="color: rgb(0, 0, 0);"><font face="Arial">Abstract: <span style="caret-color: rgb(31, 31, 31); color: rgb(31, 31, 31); orphans: 2; white-space: pre-wrap; widows: 2;">Climate sensitivity is a fundamental metric of the climate system, yet it is traditionally
diagnosed from model simulations or observed trends and therefore lacks predictive capability. In this talk, I present a recent advance that directly addresses a long-standing challenge in climate science since the Charney Report in 1979: how much warming
does the Earth’s climate produce in response to a unit external energy input at the top of the atmosphere (TOA)?</span></font></div>
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<font face="Arial">In essence, we discover from first principles that temperature feedback within an atmosphere–surface column operates as a set of feedback circuits, each governed by its own intrinsic gain less than unity, resulting in geometric compounding
amplification of input energy at individual layers and energy gain in other layers through successive feedback cycles. In particular, the surface-centered feedback circuits determine both the amplification of input energy imposed at the surface and the surface
energy gain induced by energy input in atmospheric layers. It follows that the ratio of amplified surface energy via the surface-centered temperature-feedback circuits to the initial surface energy from TOA forcing imposed at individual layers represents the
temperature-feedback amplification of surface energy per unit TOA forcing. In addition to this temperature-feedback amplification, a non-temperature-feedback amplification can be estimated from the amplification of solar energy absorbed by the surface from
downward longwave radiation at the surface in the climate mean state. Climate sensitivity then follows naturally as the ratio of the product of these two amplifications to the surface Planck feedback parameter. The climate sensitivity calculated from the ERA5
1980–2000 climate mean state is 1.166 K per 1 W m⁻² energy input at the TOA, which accurately predicts the observed warming from 1980–2000 to 2000–2020 (0.44 K versus 0.41 K observed). </font></p>
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<font face="Arial">The median warming relative to the 1980–2000 mean state under 4×CO₂ forcing imposed on 18 CMIP6 models, predicted from this sensitivity, is 6.2 K, with a full spread of 1.7 K due to intermodel differences in 4×CO₂ forcing. The median theoretically
derived pre-industrial climate sensitivity (1.0 K per 1 W m⁻²) is close to the median climate sensitivity (1.05 K per 1 W m⁻²) diagnosed from CMIP6 4×CO₂ warming relative to the pre-industrial state. The intermodel spread of the former, arising from differences
in pre-industrial mean states, is one-third of the latter. Furthermore, the median warming (5.3 K) predicted from the theoretically derived pre-industrial climate sensitivity is close to the median CMIP6 4×CO₂ warming (5.6 K) relative to the pre-industrial
mean state. Of the total uncertainty in CMIP6 4×CO₂ warming projections (3.5 K), 37% (1.3 K) can be attributed to uncertainty in the pre-industrial mean state of CMIP6 models, with the remaining 63% (2.2 K) arising from uncertainty in climate feedback strength
across models.</font></p>
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Allison Wing, Ph.D.<br>
Werner A. and Shirley B. Baum Professor<br>
Associate Professor, Department of Earth, Ocean and Atmospheric Science<br>
Florida State University<br>
awing@fsu.edu</div>
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