The Arctic is the endpoint of many climatic gradients and is presently occupied by c. 2200 vascular plant species. Glaciation started in the Middle Eocene but a significant expansion of the Greenland ice shield occurred only c. 3.2 million yr ago, leading to the expansion of the treeless circumpolar arctic tundra. Available molecular phylogenetic studies were evaluated for 148 of 374 genera occ...

Rapid loss of sea ice is opening up the Arctic Ocean to shipping, a practice that is forecasted to increase rapidly by 2050 when many models predict that the Arctic Ocean will largely be free of ice toward the end of summer. These forecasts carry considerable uncertainty because Arctic shipping was previously considered too sparse to allow for adequate validation. Here, we provide quantitative ...

The Arctic is warming about twice as rapidly as the rest of Earth. Black carbon (BC) particles are an important short-lived pollutant that explain a significant fraction of the observed Arctic warming. Most Arctic BC comes from fuel-combustion not from open fires. Arctic climate is very sensitive to the surface warming that BC causes. BC appears to warm the Arctic more than any other agent exce...

An ice-free Arctic summer would have pronounced impacts on global climate, coastal habitats, national security, and the shipping industry. Rapid and accelerated Arctic sea ice loss has placed the reality of an ice-free Arctic summer even closer to the present day. Accurate projection of the first Arctic ice-free summer year is extremely important for business planning and climate change mitigat...

With amplified warming and record sea ice loss, the Arctic is the canary of global warming. The historical Arctic warming is poorly understood, limiting our confidence in model projections. Specifically, Arctic surface air temperature increased rapidly over the early 20th century, at rates comparable to those of recent decades despite much weaker greenhouse gas forcing. Here, we show that the c...

NOAA’s recent assessment of Arctic greenness has reported a remarkable finding: the Arctic is browning (Epstein et al., 2015). Whilst a clear greening trend has been apparent for most of the satellite record’s 33 year history (indicating an increase in biomass and productivity), there is now an overall decline in greenness from 2011 to 2014. If this is a new direction of travel for arctic veget...

PREPARATORY EXPERIMENTS FOR THE CALIBRATION AND INTERPRETATION OF C1XS DATA S. Z. Weider, J. Gow, K. H. Joy, I. A. Crawford, D. R. Smith, A. D. Holland, B. M. Swinyard, The Joint UCL/Birkbeck Research School of Earth Sciences, Gower Street, London, WC1E 6BT, UK, The Rutherford Appleton Laboratory, Chilton, Oxfordshire, OX11 0QX, UK, e2v centre for electronic imaging, School of Engineering and D...

gramme to evaluate the carcinogenic risk of chemicals to humans and to pro duce monographs on individual chemicals. The Monographs programme has since been expanded to include consideration of exposures to complex mixtures of chemicals (which occur, for example, in sorne occupations and as a result of human habits) and of exposures to other agents, such as radiation and viruses. With Supplement...

Atmospheric mercury (Hg) in the Arctic shows much weaker or insignificant annual declines relative to northern midlatitudes over the past decade (2000–2009) but with strong seasonality in trends. We use a global ocean-atmosphere model of Hg (GEOS-Chem) to simulate these observed trends and determine the driving environmental variables. The atmospheric decline at northern midlatitudes can largel...

The pattern of recent surface warming observed in the Arctic exhibits both polar amplification and a strong relation with trends in the Arctic Oscillation mode of atmospheric circulation. Paleoclimate analyses indicate that Arctic surface temperatures were higher during the 20th century than during the preceding few centuries and that polar amplification is a common feature of the past. Paleocl...