Hannah Hoag

Tag: climate change

  • Arctic snow cover shows sharp decline

    Arctic snow cover shows sharp decline

    Earlier spring could spell trouble for permafrost

    Arctic snow is fading fast. June snow cover in the Northern Hemisphere has dropped by almost 18% per decade during the past 30 years, according to a study published in Geophysical Research Letters1.

    The drop in snow extent will lower the amount of sunlight reflected away from the planet — a process that has a cooling effect — by exposing darker and less reflective soil, shrubs and trees, which absorb solar radiation and re-emit the heat into the atmosphere. The change also stands to warm the permafrost, alter the timing of spring runoff into rivers and lead to earlier plant growth in spring.

    “It was a bigger number than we initially thought we might have seen, but when you look at the changes in Arctic sea ice, we would expect a similarly large number,” says Chris Derksen, a cryosphere scientist at Environment Canada in Toronto and a co-author on the paper. The swift pace of the snowmelt between 1979 and 2011 exceeds the rate of decline in Arctic sea ice, which clocked in at just under 11% per decade over the same period. September 2012 saw the lowest extent of sea ice in the satellite record — and when this year’s data were included in calculations, they revealed a 13% per decade decline in sea ice and a 21.5% per decade drop in snow cover.

    :: Get the full story at the Nature News website

  • Regime Change: Q&A with John Smol

    Nature

    A freshwater ecologist at Queen’s University in Kingston, Ontario, Canada, Smol studies lake sediments to understand climatic and environmental change. Nature Outlook asks him to share his experience.

    What can we learn from lake sediments?
    One of the biggest challenges in environmental science is the lack of long-term data, so we have to use indirect proxies. All over the planet, lakes act as passive samplers of the environment, recording information 24 hours a day. They contain biological, chemical and physical information. The deeper you go in the sediment, the older it gets. Typically, in North America you can go back 12,000 years to the last Ice Age. In ponds near the Arctic Ocean, it’s closer to 5,000 years, because before that those areas were below sea level. We focus on the changes that have occurred in the past few hundred years and compare them with the long-term record. So we can ask: is there anything peculiar going on now, or is this just part of a long-term cycle?

    What have these remote ponds told us about climate change?

    We chose shallow ponds because they would be the most sensitive. They’re the bellwethers. The palaeo-data show that some very striking ecological changes started happening since the 1800s. The most plausible interpretation is that it was climate change and that it was human related. This conclusion was very controversial when we published it in 1994 (ref.1).

    We started going to these ponds on Cape Herschel in far northern Canada in 1983. We were going up every two or three years, and we could see they were getting shallower. We thought they could eventually disappear, but none of us thought it could happen in our lifetime. By 2006, many of the ponds had gone dry. It was stunning. We wondered if it was a one-off event, but we checked the 2005 data from the probes that we had left in some of the ponds in 2004 and saw that they were dry even then. We could tell that the ponds were evaporating, not draining, because the water’s conductivity — which is proportional to the concentration of dissolved ions — had steadily been increasing. Nothing like this had ever happened before, although the drying trend has occurred since. We called it crossing the final ecological threshold.

    Keep reading this article in Nature. 

  • Frozen Assets

    Frozen Assets

    Maclean’s

    Ice cores tell the history of Canada’s climate, but now the government doesn’t want them anymore. (more…)

  • Canada’s ice cores seek new home

    Confusion over fate of valuable climate record chills researchers.

    An unusual ‘help wanted’ advertisement arrived in the inboxes of Canadian scientists last week. The e-mail asked the research community to provide new homes for an impressive archive of ice cores representing 40 years of research by government scientists in the Canadian Arctic.

    The note was sent out by Christian Zdanowicz, a glaciologist at the Geological Survey of Canada (GSC) in Ottawa. He claimed that the collection faced destruction owing to budget cuts at Natural Resources Canada (NRCan), the government department that runs the survey, and a “radical downsizing” of the Ice Core Research Laboratory. The e-mail pressed scientists at universities and other institutions to take in the ice cores before they were left to melt.

    But David Scott, director of the GSC’s northern Canada division, denies this and says that there have been no budget cuts at GSC. He says that GSC management did not approve the letter, and it contains a number of factual errors. “There is no shutdown of the ice-core facility being contemplated. We’re not actively dispersing the collection,” he says. “Nothing that meets the criterion of having scientific value would be destroyed.”

    >> Continue reading at Nature.com

    This story was posted on ScientificAmerican.com, and mentioned on Mother Jones‘ Blue Marble blog

     

     

     

     

     

  • Plants flowering later on the Tibetan Plateau

    Shorter growing season linked to warmer winters on ‘the roof of the world’.

    In many regions, climate change has advanced the timing of spring events, such as flowering or the unfolding of leaves. But the meadows and steppes of the Tibetan Plateau are bucking that trend — plants are starting to bloom later in spring, making the growing season shorter. This change could threaten the livelihood of the thousands of nomads who survive by raising cattle on the plateau.

    “I’ve worked in the Tibetan Plateau region for 25 years,” says Jianchu Xu, an ethnoecologist at the World Agroforestry Centre in Kunming, China, and a professor at the Kunming Institute of Botany of the Chinese Academy of Sciences, who led the study, published this week in theProceedings of the National Academy of Sciences. Xu says he expected that plants on the plateau would follow the same pattern of early flowering seen elsewhere. In Europe, for instance, spring flowerings in 2000 occurred about 8 days earlier than they did in 1971 on average, and autumn events, such as changes in leaf colour, about 3 days earlier.

    “But then my PhD student Haiying Yu looked at more recent data” and discovered that the opposite was the case. The finding “contradicted the linear link” that is often seen between warming temperatures and an earlier start to the growing season, Xu says.

    The group used satellite data to identify the start, end and length of the growing season for the meadow and steppe vegetation of the Tibetan Plateau between 1982 and 2006, and linked it to temperature change. During this time, the mean temperature rose about 1.4 ºC on the steppes and 1.25 ºC on the lower-lying meadows.

    The study showed an initial advance in the timing of the growing season or its ‘phenology’ for both the meadow and steppe for the first 15 years. But from 2000 until 2006 that trend was reversed. The net effect was a shortening of the growing season by about one month for steppe plants and three weeks for meadow vegetation.

    Continue reading over at Nature News.