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Reconstruction of North Atlantic surface temperature and salinity from 818 to 1780 AD

Submitted by: Geoff Zeiss - Published At: 2014-07-20 12:39 - (67 Reads)
Marine and Oceans
The Atlantic Meridional Overturning Circulation (AMOC) is a global ocean current system which transports heat and nutrients throughout most of the Earth's oceans and has a strong influence on the Earth's climate. A key driver is the the North Atlantic Current (NAC) which carries salt to the northern ocean and is essential for maintaining the high salinity of surface waters in the Nordic and Labrador seas. The sinking of highly saline water in the North Atlantic is responsible for deep water formation which the AMOC carries to the Earth's oceanic basins. In this article the authors report a reconstruction of temperature and salinity south of Iceland over about a thousand years from 818 to 1780 AD. The reconstruction found several abrupt shifts each occurring over several decades in the temperature of the NAC waters of ~3.5 ± 1.1°C between AD 818 to 1780. Some correlation between the timing of the temperature shifts in the sediment record and variations in solar irradiance was found at time scales of decades to centuries. Nature Geoscience 7, 275–278 (2014) doi:10.1038/ngeo2094(external link)

E-waste

Submitted by: Rick Higgins - Published At: 2014-07-11 15:02 - (366 Reads)
Waste
Electronic and electrical waste (e-waste for short) is reported (by the World Bank in 2012) to be growing faster than any other waste stream. Approximately 49 million tonnes of e-waste was generated globally in 2012. Of this the EU generated approximately 9.9 million tonnes, the USA 9.4 million tonnes and China 7.3 million tonnes. Three categories account for almost 90% of the generation of e-waste: large household appliances 42%, information and communication technology equipment 34% and consumer electronics 14%. E-waste comprises more than 5 per cent of all municipal waste - around the same amount as all plastic packaging. Rapid increase in the generation of e-waste is driven by the continually growing global electronics market and a concurrent rise in obsolescence rates of electronic and electrical equipment. E-waste can contain toxic materials which present significant environmental issues. It can also contain components and materials which have potential value when recycled.


How does rapid climate change occur: The Greenland ice core record

Submitted by: Geoff Zeiss - Published At: 2014-07-05 19:03 - (218 Reads)
Climate
The last glacial period (110,000 to 12,000 years ago)was punctuated by more than 20 abrupt warming events that occurred roughly every 1,500 years. In the Northern Hemisphere, these warming episodes are rapid, occurring typically over decades, followed by gradual cooling over a longer period, typically centuries. The warming events are accompanied by increased methane concentration. The relative timing of warming in Northern latitudes and in the tropics has been difficult to determine. It has also difficult to determine whether warming is led by temperature or by rising methane concentration. In this article the authors use measurements from Greenland ice cores for a single warming event to conclude that warming in the tropics and Northern latitudes occurs nearly synchronously. They also find increasing temperature and methane emissions begin at the same time. Uncertainties in dating bubbles in ice cores prevent determining with confidence whether temperature or increasing methane emissions led the warming. Within the estimated error bars, temperature could have led increasing methane emissions by up to 21 years, or alternatively methane emissions could have led increasing temperature by up to 24 years. An ice core record of near-synchronous global climate changes at the Bølling transition, Nature Geoscience 7, 459–463 (2014) doi:10.1038/ngeo2147(external link)

Amazon carbon balance is found to be sensitive to drought

Submitted by: Geoff Zeiss - Published At: 2014-02-27 01:05 - (241 Reads)
Forestry and Agriculture
The Amazon watershed stores a vast amount of carbon. Over the past two decades it has experienced increasingly higher temperatures and more frequent floods and droughts. This article reports annual carbon balances across the Amazon watershed, based on atmospheric carbon dioxide and carbon monoxide measurements for 2010 and 2011. Fortuitously 2010 was an extraordinarily dry year and 2011 was exceptionally wet in the Amazon. It was found that the carbon flux between the non-burned forest and the atmosphere was carbon neutral during the dry year. During the wet year, vegetation sequestered net 0.25 ± 0.14 petagrams of carbon per year (Pg C /yr). Nature,506,76–80 (06 February 2014) doi:10.1038/nature12957(external link)

IPCC AR5 : New Evidence about Climate Change in Earth's Oceans

Submitted by: Rick Higgins - Published At: 2014-02-10 17:48 - (443 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)