The ERA5 global reanalysis

Changes in Atmospheric Constituents and in Radiative Forcing

This chapter should be cited as: Myhre, G., D. Shindell, F.-M. Bréon, W. Collins, J. Fuglestvedt, J. Huang, D. Koch, J.-F. Lamarque, D. Lee, B. Mendoza, T. Nakajima, A. Robock, G. Stephens, T. Takemura and H. Zhang, 2013: Anthropogenic and Natural Radiative Forcing. In: Climate Change 2013: The Physical Science Basis. Contribution of Working Group I to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change [Stocker, T.F., D. Qin, G.-K. Plattner, M. Tignor, S.K. Allen, J. Boschung, A. Nauels, Y. Xia, V. Bex and P.M. Midgley (eds.)]. Cambridge University Press, Cambridge, United Kingdom and New York, NY, USA. Coordinating Lead Authors: Gunnar Myhre (Norway), Drew Shindell (USA)

Anthropogenic and Natural Radiative Forcing

The fourth version of the Community Climate System Model (CCSM4) was recently completed and released to the climate community. This paper describes developments to all CCSM components, and documents fully coupled preindustrial control runs compared to the previous version, CCSM3. Using the standard atmosphere and land resolution of 1° results in the sea surface temperature biases in the major upwelling regions being comparable to the 1.4°-resolution CCSM3. Two changes to the deep convection scheme in the atmosphere component result in CCSM4 producing El Nino–Southern Oscillation variability with a much more realistic frequency distribution than in CCSM3, although the amplitude is too large compared to observations. These changes also improve the Madden–Julian oscillation and the frequency distribution of tropical precipitation. A new overflow parameterization in the ocean component leads to an improved simulation of the Gulf Stream path and the North Atlantic Ocean meridional overturning circulati...

/pdf/the-community-climate-system-model-version-4-30sj6n6rru.pdf

The Community Climate System Model Version 4

http://joenschem.com/yahoo_site_admin/assets/docs/atkinson2000r.93190106.pdf

Atmospheric chemistry of VOCs and NOx

An array of empirical evidence in the space era, and in the past, suggests that climate responds to solar activity. The response mechanisms are thought to be some combination of direct surface heating, indirect processes involving UV radiation and the stratosphere, and modulation of internal climate system oscillations. A quantitative physical description is, as yet, lacking to explain the empirical evidence in terms of the known magnitude of solar radiative output changes and of cli- mate sensitivity to these changes. Reproducing solar-induced decadal climate change requires faster and larger responses than general circulation models allow. Nor is the indirect climatic impact of solar-induced stratospheric change adequately understood, in part because of uncertainties in the vertical coupling of the stratosphere and troposphere. Accounting for solar effects on pre-industrial surface temperatures requires larger irradiance variations than present in the contemporary database, bu te vidence for significant secular irradiance change is ambiguous. Essential for future progress are reliable, extended observations of the solar radiative output changes that produce climate forcing. Twenty-five years after the beginning of continuous monitoring of the Sun's total radiative output, the Solar Radiation and Climate Experiment (SORCE) commences a new generation of solar irradiance measurements with much expanded capabilities. Relative to historical solar observations SORCE monitors both total and spectral irradiance with significantly reduced uncertainty and increased re- peatability, especially on long time scales. Spectral coverage expands beyond UV wavelengths to encompass the visible and near-IR regions that dominate the Sun's radiative output. The space-based irradiance record, augmented now with the spectrum of the changes, facilitates improved characteri- zation of magnetic sources of irradiance variability, and the detection of additional mechanisms. This understanding provides a scientific basis for estimating past and future irradiance variations, needed for detecting and predicting climate change.

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Sorce contributions to new understanding of global change and solar variability

phase of the solar cycle there was a four to six times larger decline in ultraviolet than would have been predicted on the basis of our previous understanding. This reduction was partially compensated in the total solar output by an increase in radiation at visible wavelengths. Here we show that these spectral changes appear to have led to a significant decline from 2004 to 2007 in stratospheric ozone below an altitude of 45 km, with an increase above this altitude. Our results, simulated with a radiative-photochemical model, are consistent with contemporaneous measurements of ozone from the Aura-MLS satellite, although the short time period makes precise attribution to solar effects difficult. We also show, using the SIM data, that solar radiative forcing of surface climate is out of phase with solar activity. Currently there is insufficient observational evidence to validate the spectral variations observed by SIM, or to fully characterize other solar cycles, but our findings raise the possibility that the effects of solar variability on temperature throughout the atmosphere may be contrary to current expectations. The peak of the most recent ‘11-year’ solar cycle (identified as num

/pdf/an-influence-of-solar-spectral-variations-on-radiative-jsjxhs950c.pdf

An influence of solar spectral variations on radiative forcing of climate

[1] The Spectral Irradiance Monitor (SIM) on-board the Solar Radiation and Climate Experiment (SORCE) satellite provides the first multi-year continuous measurements of solar spectral irradiance (SSI) variability from 200–2400 nm, accounting for about 97% of the total solar irradiance (TSI). In addition to irradiance modulation from active region passage, the SSI values for wavelengths with a brightness temperature greater than 5770 K show a brightening with decreasing solar activity, whereas those with lower brightness temperatures show a dimming. These results demonstrate that different parts of the solar atmosphere contribute differently to the TSI with the behavior in the deep photospheric layers giving an opposing and nearly compensating trend to that in the upper photospheric and lower chromospheric layers. These findings need to be incorporated into Earth-climate assessments since the solar forcing induced by these differential trends are inherently different from the relatively flat spectral contributions employed in the IPCC assessments.

https://www.leif.org/EOS/2008GL036797.pdf

Trends in solar spectral irradiance variability in the visible and infrared

[1] The IHY2007 Whole Heliosphere Interval (WHI) for solar Carrington Rotation 2068 (20 March to 16 April 2008) has been very successful in obtaining a wide variety of solar, heliospheric, and planetary observations during times of solar cycle minimum conditions. One of these efforts is the generation of solar irradiance reference spectra (SIRS) from 0.1 nm to 2400 nm using a combination of satellite and sounding rocket observations. These reference spectra include daily satellite observations from TIMED Solar Extreme ultraviolet Experiment (SEE) and Solar Radiation and Climate Experiment (SORCE) instruments. The extreme ultraviolet range is also improved with higher spectral resolution observations using the prototype SDO Extreme ultraviolet Variability Experiment (EVE) aboard a sounding rocket launched on 14 April 2008. The SIRS result is an important accomplishment in that it is the first data set to have simultaneous measurements over the full spectral coverage up to 2400 nm during solar cycle minimum conditions.

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Jerald W. Harder

Papers

Sorce contributions to new understanding of global change and solar variability

An influence of solar spectral variations on radiative forcing of climate

Trends in solar spectral irradiance variability in the visible and infrared

Solar Irradiance Reference Spectra (SIRS) for the 2008 Whole Heliosphere Interval (WHI)

Measured and modeled trends in solar spectral irradiance variability in the visible and infrared