Summary for policymakers Technical summary 1. The climate system - an overview 2. Observed climate variability and change 3. The carbon cycle and atmospheric CO2 4. Atmospheric chemistry and greenhouse gases 5. Aerosols, their direct and indirect effects 6. Radiative forcing of climate change 7. Physical climate processes and feedbacks 8. Model evaluation 9. Projections of future climate change 10. Regional climate simulation - evaluation and projections 11. Changes in sea level 12. Detection of climate change and attribution of causes 13. Climate scenario development 14. Advancing our understanding Glossary Index Appendix.

Climate change 2001: the scientific basis

The planetary boundaries framework defines a safe operating space for humanity based on the intrinsic biophysical processes that regulate the stability of the Earth system. Here, we revise and update the planetary boundary framework, with a focus on the underpinning biophysical science, based on targeted input from expert research communities and on more general scientific advances over the past 5 years. Several of the boundaries now have a two-tier approach, reflecting the importance of cross-scale interactions and the regional-level heterogeneity of the processes that underpin the boundaries. Two core boundaries—climate change and biosphere integrity—have been identified, each of which has the potential on its own to drive the Earth system into a new state should they be substantially and persistently transgressed.

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Planetary boundaries: Guiding human development on a changing planet

Changes in Atmospheric Constituents and in Radiative Forcing

Black carbon aerosol plays a unique and important role in Earth's climate system. Black carbon is a type of carbonaceous material with a unique combination of physical properties. This assessment provides an evaluation of black-carbon climate forcing that is comprehensive in its inclusion of all known and relevant processes and that is quantitative in providing best estimates and uncertainties of the main forcing terms: direct solar absorption; influence on liquid, mixed phase, and ice clouds; and deposition on snow and ice. These effects are calculated with climate models, but when possible, they are evaluated with both microphysical measurements and field observations. Predominant sources are combustion related, namely, fossil fuels for transportation, solid fuels for industrial and residential uses, and open burning of biomass. Total global emissions of black carbon using bottom-up inventory methods are 7500 Gg yr−1 in the year 2000 with an uncertainty range of 2000 to 29000. However, global atmospheric absorption attributable to black carbon is too low in many models and should be increased by a factor of almost 3. After this scaling, the best estimate for the industrial-era (1750 to 2005) direct radiative forcing of atmospheric black carbon is +0.71 W m−2 with 90% uncertainty bounds of (+0.08, +1.27) W m−2. Total direct forcing by all black carbon sources, without subtracting the preindustrial background, is estimated as +0.88 (+0.17, +1.48) W m−2. Direct radiative forcing alone does not capture important rapid adjustment mechanisms. A framework is described and used for quantifying climate forcings, including rapid adjustments. The best estimate of industrial-era climate forcing of black carbon through all forcing mechanisms, including clouds and cryosphere forcing, is +1.1 W m−2 with 90% uncertainty bounds of +0.17 to +2.1 W m−2. Thus, there is a very high probability that black carbon emissions, independent of co-emitted species, have a positive forcing and warm the climate. We estimate that black carbon, with a total climate forcing of +1.1 W m−2, is the second most important human emission in terms of its climate forcing in the present-day atmosphere; only carbon dioxide is estimated to have a greater forcing. Sources that emit black carbon also emit other short-lived species that may either cool or warm climate. Climate forcings from co-emitted species are estimated and used in the framework described herein. When the principal effects of short-lived co-emissions, including cooling agents such as sulfur dioxide, are included in net forcing, energy-related sources (fossil fuel and biofuel) have an industrial-era climate forcing of +0.22 (−0.50 to +1.08) W m−2 during the first year after emission. For a few of these sources, such as diesel engines and possibly residential biofuels, warming is strong enough that eliminating all short-lived emissions from these sources would reduce net climate forcing (i.e., produce cooling). When open burning emissions, which emit high levels of organic matter, are included in the total, the best estimate of net industrial-era climate forcing by all short-lived species from black-carbon-rich sources becomes slightly negative (−0.06 W m−2 with 90% uncertainty bounds of −1.45 to +1.29 W m−2). The uncertainties in net climate forcing from black-carbon-rich sources are substantial, largely due to lack of knowledge about cloud interactions with both black carbon and co-emitted organic carbon. In prioritizing potential black-carbon mitigation actions, non-science factors, such as technical feasibility, costs, policy design, and implementation feasibility play important roles. The major sources of black carbon are presently in different stages with regard to the feasibility for near-term mitigation. This assessment, by evaluating the large number and complexity of the associated physical and radiative processes in black-carbon climate forcing, sets a baseline from which to improve future climate forcing estimates.

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Bounding the role of black carbon in the climate system: A scientific assessment

Human activities are releasing tiny particles (aerosols) into the atmosphere. These human-made aerosols enhance scattering and absorption of solar radiation. They also produce brighter clouds that are less efficient at releasing precipitation. These in turn lead to large reductions in the amount of solar irradiance reaching Earth's surface, a corresponding increase in solar heating of the atmosphere, changes in the atmospheric temperature structure, suppression of rainfall, and less efficient removal of pollutants. These aerosol effects can lead to a weaker hydrological cycle, which connects directly to availability and quality of fresh water, a major environmental issue of the 21st century.

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Aerosols, climate, and the hydrological cycle

. The impact of anthropogenic absorbing aerosols (such as soot) on the climate over the Indian region has been studied using the NCMRWF general circulation model. The absorbing aerosols increase shortwave radiative heating of the lower troposphere and reduce the heating at the surface. These effects have been incorporated as heating of the lower troposphere (up to 700hPa) and cooling over the continental surface based on INDOEX measurements. The heating effect is constant in the pre-monsoon season and reduces to zero during the monsoon season. It is shown that even in the monsoon season when the aerosol forcing is zero, there is an overall increase in rainfall and a reduction in surface temperature over the Indian region. The rainfall averaged over the Tropics shows a small reduction in most of the months during the January to September period. The impact of aerosol forcing, the model's sensitivity to this forcing and its interaction with model-physics has been studied by changing the cumulus parameterization from the Simplified Arakawa-Schubert (SAS) scheme to the Kuo scheme. During the pre-monsoon season the major changes in precipitation occur in the oceanic Inter Tropical Convergence Zone (ITCZ), where both the schemes show an increase in precipitation. This result is similar to that reported in Chung2002. On the other hand, during the monsoon season the changes in precipitation in the continental region are different in the SAS and Kuo schemes. It is shown that the heating due to absorbing aerosols changes the vertical moist-static stability of the atmosphere. The difference in the precipitation changes in the two cumulus schemes is on account of the different responses in the two parameterization schemes to changes in vertical stability. Key words. Atmospheric composition and structure (aerosols and particles) – Meteorology and atmospheric dynamics (tropical meteorology; precipitation)

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Impact of absorbing aerosols on the simulation of climate over the Indian region in an atmospheric general circulation model

Microbial biofilms on the surfaces of man–made structures in the marine environment cause serious problems for marine industries. Currently used heavy metal-based toxic antifoulants has created environmental problem, which mandates the necessity of “eco-friendly” antifoulants. Marine-based microbial secondary metabolites are promising potential sources of nontoxic antifouling compounds. In the present study, we have investigated the antifouling potentials of bacterial red pigment prodigiosin extracted from Serratia marcescens CMST 07. Prodigiosin was showed high antifouling activity against marine fouling bacteria like Alteromonas sp. and Gallionella sp. minimum inhibitory concentration (MIC) and minimum bactericidal concentration (MBC) of the pigment was about 6.75 and 12.5 μg/ml respectively against Alteromonas sp. LD50 of prodigiosin against artemia (artemia toxicity study) was about 50 μg/ml. Prodigiosin significantly (P < 0.01) inhibits cyanobacterial adhesion on glass surface, which augments the possibility of using bacterial pigments as the source of antifouling compounds for controlling the fouling problem in the marine environments.

https://www.springer.com/cda/content/document/cda_downloaddocument/9788132210863-c2.pdf?SGWID=0-0-45-1387768-p174887102

Antifouling Activity of Prodigiosin from Estuarine Isolate of Serratia marcescens CMST 07

The seasonal variability in fouling community recruitment on submerged artificial substratum was studied in Kudankulam coastal water, Gulf of Mannar, East coast of India for a period of two years, from May 2003 to April 2005. The results indicated that the fouling community recruitment occurred throughout the year with varying intensities. Barnacles, ascidians, polychaetes, bivalves and seaweeds were the major fouling groups observed from the test panels. Maximum fouling biomass of 9.17 g dm −2 was observed during August 2004 and a minimum value of 0.233 g dm −2 in February 2004. The biomass build-up on test panels was relatively high during the premonsoon season and low during the postmonsoon months. The number of barnacles settled on the panels varied from 1 to 4460 no. dm −2 . The maximum percentage of the ascidian coverage (72%) on test panels was observed during March 2005. In general, July–December was the period of intense recruitment for barnacles and March–May was the period for ascidians.

Seasonal variability in the recruitment of macrofouling community in Kudankulam waters, east coast of India

Satellite‐ (MODIS onboard TERRA satellite) measured regional dust distribution has been used in this paper to examine the effect of dust aerosols on top of the atmosphere (TOA) albedo and it was found they have significant impact, especially over deserts, where surface reflection is high. With increasing dust load, TOA albedo was found to decrease significantly and it was observed that over deserts, TOA albedo becomes less than that at the surface (as much as 15% in near infrared) due to absorption by dust. The temporal variations of aerosol properties were examined at three representative locations: northern Africa (10° N–20° N; 20° E–30° E) and Saudi Arabia (19° N–24° N; 53° E–58° E) (both of which are influenced heavily by dust); and southern Africa (10° S–20° S; 20° E–30° E) (where the influence of dust is seasonal). Over northern Africa, optical depth was maximum (∼0.6) during the June–August period and lower (0.3–0.6) during the rest of the year. The aerosol fine mode fraction (AFMF) was, in general...

Impact of dust aerosols on Earth-atmosphere clear-sky albedo and its short wave radiative forcing over African and Arabian regions

Aerosol spectral optical depth (AOD) measurements were made covering three years (2001, 2002 and 2003) at an urban continental location,Bangalore (13degrees N, 77.6degrees E) in India. These ground-based observations have shown that AODs reach a maximum during April (similarto0.5 at 500 nm) and minimum during the November to January period(similar to0.2). The Angstrom wavelength exponent (ce) was - LI during the dry season (December to April), which, in conjunction with the highoptical depth indicates significant anthropogenic influence. Seasonal variations in AODs appear to have an association with monsoon rainfall.Large AODs (a-1.4) were observed during the rain-deficit summer monsoon season (SMS) of 2002, which persisted for more than six months.Enhancement in AODs during SMS 2002 was similar to0.15 (at 500 nm),compared to 2001 and 2003.

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Sathianeson Satheesh

Papers

Impact of absorbing aerosols on the simulation of climate over the Indian region in an atmospheric general circulation model

Antifouling Activity of Prodigiosin from Estuarine Isolate of Serratia marcescens CMST 07

Seasonal variability in the recruitment of macrofouling community in Kudankulam waters, east coast of India

Impact of dust aerosols on Earth-atmosphere clear-sky albedo and its short wave radiative forcing over African and Arabian regions

Large aerosol optical depths observed at an urban location in southern India associated with rain-deficit summer monsoon season