A5061188805- Atmospheric Ozone and Climate
- Atmospheric and Environmental Gas Dynamics
- Atmospheric chemistry and aerosols
- Solar and Space Plasma Dynamics
- Climate variability and models
- Atmospheric aerosols and clouds
- Solar Radiation and Photovoltaics
- Meteorological Phenomena and Simulations
- Ionosphere and magnetosphere dynamics
- Calibration and Measurement Techniques
- Global Energy and Sustainability Research
- Astro and Planetary Science
- Oceanographic and Atmospheric Processes
- Marine and coastal ecosystems
- Spectroscopy and Laser Applications
- Geology and Paleoclimatology Research
- Geophysics and Gravity Measurements
- Fluid Dynamics and Turbulent Flows
- Planetary Science and Exploration
- Climate Change and Geoengineering
- Complex Systems and Time Series Analysis
- Advanced Thermodynamics and Statistical Mechanics
- Marine and environmental studies
- Urban Heat Island Mitigation
- Climate Change Policy and Economics
Imperial College London
2014-2024
Columbia University
2023
Imperial Valley College
1996-2023
Isle of Wight NHS Trust
2021
Imperial Consultants
2020
Institut d'Estudis Espacials de Catalunya
2015
Kyung Hee University
2014
National Centre for Atmospheric Science
2010
University of Reading
2000-2010
Uganda National Meteorological Authority
2010
[1] Understanding the influence of solar variability on Earth's climate requires knowledge variability, solar-terrestrial interactions, and mechanisms determining response system. We provide a summary our current understanding in each these three areas. Observations for Sun's are described, including irradiance variations both decadal centennial time scales their relation to galactic cosmic rays. Corresponding observations associated ozone, temperatures, winds, clouds, precipitation,...
A general circulation model that simulated changes in solar irradiance and stratospheric ozone was used to investigate the response of atmosphere 11-year activity cycle. At maximum, a warming summer stratosphere found strengthen easterly winds, which penetrated into equatorial upper troposphere, causing poleward shifts positions subtropical westerly jets, broadening tropical Hadley circulations, storm tracks. These effects are similar to, although generally smaller magnitude than, those...
Abstract. Ozone forms in the Earth's atmosphere from photodissociation of molecular oxygen, primarily tropical stratosphere. It is then transported to extratropics by Brewer–Dobson circulation (BDC), forming a protective ozone layer around globe. Human emissions halogen-containing ozone-depleting substances (hODSs) led decline stratospheric until they were banned Montreal Protocol, and since 1998 upper stratosphere rising again, likely recovery halogen-induced losses. Total column...
The brightness of the Sun varies on all timescales which it has been observed, and there is increasing evidence that this an influence climate. amplitudes such variations depend wavelength possibly timescale. Although many aspects variability are well established, exact magnitude secular (going beyond a solar cycle) spectral dependence under discussion. main drivers thought to be magnetic features at surface. climate response can be, global scale, largely accounted for by simple energetic...
Abstract Global climate models are central tools for understanding past and future change. The assessment of model skill, in turn, can benefit from modern data science approaches. Here we apply causal discovery algorithms to sea level pressure a large set simulations and, as proxy observations, meteorological reanalyses. We demonstrate how the resulting networks (fingerprints) offer an objective pathway process-oriented evaluation. Models with fingerprints closer observations better...
How do we halt global warming? Reaching net zero carbon dioxide (CO 2 ) emissions is understood to be a key milestone on the path safer planet. But how confident are that when stop emissions, also The Zero Emissions Commitment (ZEC) quantifies much warming or cooling can expect following complete cessation of anthropogenic CO emissions. To date, best estimate by Intergovernmental Panel Climate Change (IPCC) Sixth Assessment Report change, though with substantial uncertainty. In this article,...
The absolute value of total solar irradiance is not known to better than ca.0.3% but measurements from satellite instruments over the past two cycles have shown that it varies by ca.0.1% on this time-scale. Over longer periods its has been reconstructed using proxy measures activity, and these suggest during Maunder minimum in activity late 17th century was 3−4 W m−2 lower at present. Observational data Sun influenced temperatures decadal, centennial millennial time-scales, radiative forcing...
Abstract A multiple regression analysis of the NCEP–NCAR reanalysis dataset shows a response to increased solar activity weakening and poleward shift subtropical jets. This signal is separable from other influences, such as those El Niño–Southern Oscillation (ENSO) North Atlantic (NAO), very similar that seen in previous studies using global circulation models (GCMs) effects an increase spectral irradiance. The stratospheric (volcanic) aerosol found data be equatorward GCM influence also...
Variations in solar activity, at least as observed numbers of sunspots, have been apparent since ancient times but to what extent variability may affect global climate has far more controversial. The subject had and out fashion for two centuries the current need distinguish between natural anthropogenic causes change brought it again forefront meteorological research. absolute radiometers carried by satellites late 1970s produced indisputable evidence that total irradiance varies...
Abstract Estimates of annual‐mean stratospheric temperature trends over the past twenty years, from a wide variety models, are compared both with each other and observed cooling seen in trend analyses using radiosonde satellite observations. The modelled driven by changes ozone (either imposed observations or calculated model), carbon dioxide relatively well‐mixed greenhouse gases, water vapour. comparison shows that whilst models generally simulate similar patterns vertical profile...
Abstract A simplified general circulation model has been used to investigate the chain of causality whereby changes in tropospheric and temperature are produced response stratospheric heating perturbations. Spinup ensemble experiments have performed examine evolution such The primary aim these is possible mechanisms a changing solar activity over 11-yr cycle could be equatorial lower stratosphere. This study therefore focuses on perturbation which largest tropics. For comparison, also...
Abstract A two‐dimensional circulation model is used to investigate the possible perturbation of ozone layer by CO 2 and chlorofluorocarbons (CFC's). Four experiments are described: a control run; run including increasing levels up 625 ppm; source chlorine compounds from CFCs; coupled due both CFC's. The dynamical chemical behaviour runs described. reaffirms conclusions earlier with this (Harwood Pyle 1980) that summer stratopause very close radiative equilibrium. strength polar night jet...
A number of studies have demonstrated the importance ozone in climate change simulations, for example concerning global warming projections and atmospheric dynamics. However, fully interactive chemistry schemes needed calculating changes are computationally expensive. Climate modelers therefore often use climatological fields, which typically neither consistent with actual state simulated by each model nor specific scenario. This limitation applies particular to standard modeling experiments...
Abstract A general‐circulation model (GCM) is used to investigate the impact of 11‐year solar‐activity cycle on climate lower atmosphere. Solar forcing represented by changes in both incident irradiance and stratospheric ozone concentrations. Experiments are carried out with realistic factor‐ten enhanced solar based two‐dimensional photochemical results loosely Total Ozone Mapping Spectrometer column data. pattern response, consistent across all experiments, found which tropical Hadley cells...
Abstract. We identify solar cycle signals in 155 years of global sea level pressure (SLP) and surface temperature (SST) data using a multiple linear regression approach. In SLP we find the North Pacific statistically significant weakening Aleutian Low northward shift Hawaiian High response to higher activity, confirming results previous authors different techniques. also weak but broad reduction across equatorial Pacific. SST El Niño-like pattern tropics for year period, unlike strong La...
Abstract Up to now our understanding of the 11 year ozone solar cycle signal (SCS) in upper stratosphere has been largely based on Stratospheric Aerosol and Gas Experiment (SAGE) II (v6.2) data record, which indicated a large positive could not be reproduced by models, calling into question chemistry stratosphere. Here we present an analysis new v7.0 SAGE shows smaller SCS, due more realistic ozone‐temperature anticorrelation. New simulations from state‐of‐art 3‐D chemical transport model...
Many applications of Earth‐observing satellite radiometer measurements in the visible and near infra‐red require surface reflectances, necessitating use atmospheric correction algorithms. Performing these corrections usually requires assumption Lambertian surfaces, a limitation that becomes serious with new generation multi‐look radiometers. In this letter, we present test theoretically multiple‐channel approximation does not assume surface, but instead assumes wavelength dependence shape...
The mega‐eruption of Toba, Sumatra, occurred around 73 Ka ago, during the onset a glaciation Late Quaternary. This coincidence combined with unprecedented amount sulphur released by this volcano has led to hypothesis that Toba sulphate aerosols caused transient surface cooling which may have contributed shift climate system. Because self limiting effect gravitational sedimentation, climatic impact extremely large injections into stratosphere are thought be rather limited. Here we present...
Abstract We present results of multiple regressions the leading mode atmospheric variability at southern high latitudes: Southern Annular Mode (SAM). It is regressed against indices with large interannual variability, and one several trend in order to determine which term gives optimum fit. use SAM sea‐level pressure from station data provide a long time series, 1957 2005. The regression are stratospheric volcanic aerosol, solar activity, quasi‐biennial oscillation (QBO), El Niño–Southern...