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The cryosphere and climate change - An EC perspective on the evidence presented in IPCC's 5th Assessment Report

Submitted by: Rick Higgins - Published At: 2014-11-16 11:08 - (1119 Reads)
Climate
The term cryosphere refers to those parts of the Earth’s surface where water is in solid form. This includes ice in glaciers, ice sheets and sea ice as well as permafrost (frozen ground) and snow. The cryosphere plays a major role in the global climate system and impacts such critical environmental factors as sea level, the water cycle, surface energy budgets and methane production. The IPCC 5th Assessment Report (AR5) focuses on the cryosphere as one of its main themes. The report (AR5 chapter 4) concludes (with high confidence) that over the last two decades glaciers have continued to shrink almost worldwide, the Greenland and Antarctic ice sheets have been losing mass and Arctic sea ice and Northern Hemisphere spring snow cover have continued to decrease in extent. The report also concludes that multiple lines of evidence support very substantial Arctic warming since the mid-20th century. In addition there is more data every year indicating a continuing increase in permafrost thawing (which leads to the release of methane). IPCC AR5, Chapter 4 - Cryosphere(external link)
This article is one of a series of eight providing an EnvironmentCounts.org (EC) perspective on various aspects of IPCC's AR5. Each article focuses on the primary data and related evidence presented and specifically excludes coverage of projections, as per EC's editorial policy and guidelines.

The oceans and climate change - An EC perspective on the evidence presented in IPCC's 5th Assessment Report

Submitted by: Rick Higgins - Published At: 2014-11-16 11:02 - (534 Reads)
Marine and Oceans
The Fifth Assessment Report (AR5) of the IPCC states there is strong evidence that four global measures of ocean change have increased since the 1950s: the inventory of anthropogenic carbon dioxide, global mean sea level, upper ocean heat content, and the salinity contrast between regions of high and low sea surface salinity.
About 93% of the excess heat energy stored by the earth over the last 50 years is found in the ocean and changes in ocean heat content dominate changes in the global energy inventory. The report states that global mean sea level (GMSL) rose by 0.19 (0.17 to 0.21) m over the period 1901 to 2010. The rate of sea level rise since the mid-19th century has been larger than the mean rate during the previous two millennia (high confidence). The report concludes with high confidence that the observed patterns of change in the subsurface ocean are consistent with changes in the surface ocean in response to climate change and natural variability and with known physical and biogeochemical processes in the ocean. IPCC AR5 Chapter 3: Observations: Ocean(external link)

This article is one of a series of eight providing an EnvironmentCounts.org (EC) perspective on various aspects of IPCC's AR5. Each article focuses on the primary data and related evidence presented and specifically excludes coverage of projections, as per EC's editorial policy and guidelines.

Sea level change - An EC perspective on the evidence presented in IPCC's 5th Assessment Report

Submitted by: Rick Higgins - Published At: 2014-11-16 10:51 - (249 Reads)
Marine and Oceans
More than seventy percent of the World’s surface is covered by water. Between 1901 and 2010 AR5 states that it is “very likely” the global mean rate of sea level rise was 1.7 (1.5 to 1.9) millimetres per year (mm/yr) for a total sea level rise of 0.19 (0.17 to 0.21) metres (m) or 19 centimetres (cm). In recent decades global mean sea level (GMSL) has continued to rise, and at an increased rate. Between 1993 and 2010, the rate was 3.2 (2.8 to 3.6) mm/yr.

For the first time observations are now available for each of the contributions to the observed GMSL change (from such contributing factors as thermal expansion, melting glaciers and ice sheets), as a result of improved and new observations of the ocean since the introduction of satellite radar altimetry in 1993. Observations indicate that 90% of anthropogenic heat added to the climate system has been in the oceans.

During the last interglacial period (~129,000 to 116,000 years ago) global mean sea level (GMSL) was, for several thousand years, between a minimum of 5m ("very high confidence") and a maximum of 10m ("high confidence") higher than present. AR5 concludes with “high confidence” that sea level data indicate a transition in the late 19th century to the early 20th century from relatively low mean rates of rise over the previous two millennia to higher rates of rise. Over the past 2,000 years there is "medium confidence" that fluctuations in GMSL did not exceed ~ +/- 0.25m (or 25cm). Sea Level Change(external link).

This article is one of a series of eight providing an EnvironmentCounts.org (EC) perspective on various aspects of IPCC's AR5. Each article focuses on the primary data and related evidence presented and specifically excludes coverage of projections, as per EC's editorial policy and guidelines.

New Evidence about Earth's carbon cycle and climate change - IPCC 5th ASSESSMENT Report

Submitted by: Geoff Zeiss - Published At: 2014-09-23 11:31 - (290 Reads)
Climate
The Earth's carbon cycle is represented by reservoirs of carbon in the atmosphere, on land, and in the oceans. These reservoirs exchange carbon with each other. The atmosphere exchanges CO2 with the land and the oceans. On land the important processes are plant photosynthesis, which removes CO2 from the atmosphere, and plant respiration which adds CO2 to the atmosphere.

CO2 from the atmosphere dissolves in the ocean in the form of dissolved inorganic carbon (e.g. carbonates). Dissolved carbon from the oceans is also ventilated into the atmosphere. Before the Industrial Era around 1750, these processes between the atmosphere and land and the oceans nearly balanced each other and atmospheric carbon, mostly CO2 and methane remained constant.

Since around 1750 the increase in CO2 emissions from fossil fuel burning and from land use change have been the dominant cause of the observed increase in atmospheric CO2 concentration.

Overall the net response to rising CO2 is to increase cumulative land and ocean uptake. The pre-industrial atmosphere-land carbon balance was very close with a net flux of about 1.7 PgC/yr (1 PgC is one trillion tonnes of carbon) being transferred annually to land. The anthropogenic effect has increased that by 2.6 PgC/yr to 4.2 PgC/yr.

With respect to atmosphere-oceans carbon exchange the net anthropogenic effect is that since 1750 the oceans have become a carbon sink absorbing significant quantities of CO2 from the atmosphere with a net balance of 1.6 PgC/yr being transferred from the atmosphere to the oceans. Atmospheric CO2 continues to increase by about 3.1 PgC/yr because the increased uptake of CO2 by land and the oceans is not sufficient to compensate for fossil fuel combustion and land use change.
IPCC Fifth Assessment Report Climate Change 2013: The Physical Science Basis Chapter 6 Carbon and Other Biogeochemical Cycles(external link)

New evidence about anthropogenic aerosols and climate change - IPCC 5th ASSESSMENT Report

Submitted by: Geoff Zeiss - Published At: 2014-09-15 17:28 - (259 Reads)
Climate
The atmosphere is composed mostly of gases, but it also contains liquid and solid matter in the form of particles. Water aerosols are called clouds. The main constituents of non-water atmospheric aerosols are inorganic particles such as sulphate, nitrate, ammonium, and sea salt, organic aerosols (OA), black carbon (BC) from fossil fuel combustion, mineral dust (mostly desert dust) and primary biological aerosol particles (PBAPs)such as bacteria, fungal spores, and pollen. The majority of black carbon, sulphate, nitrate and ammonium come from anthropogenic sources, whereas sea salt, most mineral dust and PBAPs are predominantly of natural origin. Natural sulfur aerosols (sulfates) are formed from the sulfur dioxide(SO2) ejected by volcanoes.

The primary net effect of aerosol particles interacting with solar radiation (short wavelengths) is reflectance which cools the planet. But aerosol particles also interact with heat (long wavelengths) emanating from the Earth with a net warming effect. Aerosols can also serve as cloud condensation nuclei (CCN) and ice nuclei (IN) which contribute to cloud formation, but the mechanisms by which aerosols affect clouds and precipitation is very poorly understood.

Anthropogenic aerosols have been the strongest contributor to climate cooling except for brief periods with large volcanic eruptions. The cooling effect from anthropogenic aerosols has also grown stronger with time as industrial production has increased.

The major conclusion of AR5 is that aerosols are the dominant contributor to uncertainty in the net effect of anthropogenic sources during the Industrial Era. However, despite the large uncertainty range in the various contributions, there is a high confidence that aerosols have offset a substantial portion of greenhouse gas climate warming. IPCC Fifth Assessment Report Climate Change 2013: The Physical Science Basis Chapters 7 and 8(external link)