Political Ecology

Here we report microbiological, molecular and hydrogen isotopic evidence from lake sediments in the Northern Line Islands, Galápagos and Palau indicating that the Pacific intertropical convergence zone was south of its modern position for most of the past millennium, by as much as 500 km during the Little Ice Age. A colder Northern Hemisphere at that time, possibly resulting from lower solar irradiance, may have driven the intertropical convergence zone south. We conclude that small changes in Earth’s radiation budget may profoundly affect tropical rainfall.

doi:10.1038/ngeo554

Southward movement of the Pacific intertropical convergence zone : AD: [thinsp]1400-1850 : Abstract : Nature Geoscience

Background: The vertebrate aryl hydrocarbon receptor (AHR) is a ligand-activated transcription factor that regulates cellular responses to environmental polycyclic and halogenated compounds. The naive receptor is believed to reside in an inactive cytosolic complex that translocates to the nucleus and induces transcription of xenobiotic detoxification genes after activation by ligand.Objectives: We conducted an integrative genomewide analysis of AHR gene targets in mouse hepatoma cells and determined whether AHR regulatory functions may take place in the absence of an exogenous ligand.Methods: The network of AHR-binding targets in the mouse genome was mapped through a multipronged approach involving chromatin immunoprecipitation/chip and global gene expression signatures. The findings were integrated into a prior functional knowledge base from Gene Ontology, interaction networks, Kyoto Encyclopedia of Genes and Genomes pathways, sequence motif analysis, and literature molecular concepts.Results: We found the naive receptor in unstimulated cells bound to an extensive array of gene clusters with functions in regulation of gene expression, differentiation, and pattern specification, connecting multiple morphogenetic and developmental programs. Activation by the ligand displaced the receptor from some of these targets toward sites in the promoters of xenobiotic metabolism genes.Conclusions: The vertebrate AHR appears to possess unsuspected regulatory functions that may be potential targets of environmental injury.

doi:10.1289/ehp.0800485

Genomewide Analysis of Aryl Hydrocarbon Receptor Binding Targets Reveals an Extensive Array of Gene Clusters that Control Morphogenetic and Developmental Programs

Scientists have recently acknowledged that some degree of global warming is inevitable. Given this fact, efforts to mitigate greenhouse gas emissions are beginning to share the global policy stage with initiatives for adapting to the climate change that is already under way, a shift that U.S. policy makers have been slow to embrace. Climate change is expected to affect different regions in different ways, making adaptation a local issue. Yet a lack of scientific information makes it difficult to predict local impacts, hampering efforts by local, state, and regional governments to prepare. As a way to begin assessing local challenges, a panel of the National Research Council has proposed the use of university-based scientists to help decision makers evaluate local impacts and response options in a program similar to the cooperative extension system.

Beyond Mitigation: Planning for Climate Change Adaptation

So what strategy offers the most climate mitigation bang for the investment buck? Among 18 experts questioned on mitigation strategies by the U.S. Governmental Accountability Office for its May 2008 report, Climate Change: Expert Opinion on the Economics of Policy Options to Address Climate Change, 7 preferred a tax, and 11 preferred some form of cap and trade. Despite that disagreement, one message came through loud and clear: 16 of the 18 experts urged adoption of some form of carbon pricing as soon as possible.

Climate Change Abatement Strategies: Which Way Is the Wind Blowing?

The global voluntary market for carbon credits roughly doubled in 2008, according to a report by Ecosystem Marketplace and New Carbon Finance. For the year, 123.4 million metric tons of carbon dioxide equivalent (MtCO2e) were transacted, with a total estimated value of $705 million USD. Transactions for 2007 totaled 65 million tons, valued at $331 million USD. The report estimates U.S.-originating 2008 offset volume at 31.4 MtCO2e.The average price for voluntary credits in 2008 was $7.34/tCO2e, an increase of 20% from $6.10 in 2007 and 79% from $4.10 in 2006, according to the report. A carbon credit, also known as an offset, is a tradable commodity representing a unit of carbon dioxide emissions reduction or avoidance. Typically, one credit/offset represents a reduction or avoidance of one metric ton of carbon dioxide or carbon dioxide equivalent (CO2e).

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