Jennifer Marohasy

a forum for the discussion of issues concerning the natural environment

Archives for February 5, 2008

Robber Flies

By

Robber Fly.jpg

Beauty, it is said, is in the eye of the beholder … so behold, the beautiful Robber Fly. These predatory insects launch into attack from an established perch and catch their prey on the wing. Strong, heavily barbed legs grasp the prey, which is lanced with modified mouthparts in the form of a stabbing proboscis, injecting saliva containing neurotoxic and proteolytic enzymes.

Robber Flies are somewhat intimidating in close proximity. Unlike March Flies, they do not seem interested in human fare, but they are invariably given wide berth, nonetheless.

I associate the presence of Robber Flies on nocturnal vegetation with the change from cold and secretive to hot and revealing.

New Paper Puts Modern Arctic Temperatures into Perspective

By

A new paper published in Climate Dynamics claims a temperature trend of -0.3°C over the last 1,500 years in an Arctic location. The paper by Håkan Grudd is entitled: ‘Torneträsk tree-ring width and density ad 500–2004: a test of climatic sensitivity and a new 1500-year reconstruction of north Fennoscandian summers’

The Abstract states:

This paper presents updated tree-ring width (TRW) and maximum density (MXD) from Torneträsk in northern Sweden, now covering the period ad 500–2004. By including data from relatively young trees for the most recent period, a previously noted decline in recent MXD is eliminated. Non-climatological growth trends in the data are removed using Regional Curve Standardization (RCS), thus producing TRW and MXD chronologies with preserved low-frequency variability. The chronologies are calibrated using local and regional instrumental climate records. A bootstrapped response function analysis using regional climate data shows that tree growth is forced by April–August temperatures and that the regression weights for MXD are much stronger than for TRW. The robustness of the reconstruction equation is verified by independent temperature data and shows that 63–64% of the instrumental inter-annual variation is captured by the tree-ring data. This is a significant improvement compared to previously published reconstructions based on tree-ring data from Torneträsk. A divergence phenomenon around ad 1800, expressed as an increase in TRW that is not paralleled by temperature and MXD, is most likely an effect of major changes in the density of the pine population at this northern tree-line site. The bias introduced by this TRW phenomenon is assessed by producing a summer temperature reconstruction based on MXD exclusively. The new data show generally higher temperature estimates than previous reconstructions based on Torneträsk tree-ring data. The late-twentieth century, however, is not exceptionally warm in the new record: On decadal-to-centennial timescales, periods around ad 750, 1000, 1400, and 1750 were equally warm, or warmer. The 200-year long warm period centered on ad 1000 was significantly warmer than the late-twentieth century (p < 0.05) and is supported by other local and regional paleoclimate data. The new tree-ring evidence from Torneträsk suggests that this “Medieval Warm Period” in northern Fennoscandia was much warmer than previously recognized. The paper concludes: The Tornetra¨sk records of MXD and TRW are updated to AD 2004. By including MXD data from relatively young trees in the most recent period, a previously noted apparent loss of sensitivity to temperature is eliminated. These new data enable a much improved reconstruction of summer temperature for the last 1,500 years in northern Fennoscandia. Previous climate reconstructions based on tree-ring data from Tornetra¨sk were biased by a divergence phenomenon in TRW around AD 1800 and therefore show erroneously low temperature estimates in the earlier part of the records. Tornetra¨sk MXD does not show this ‘‘divergence problem’’ and hence produces robust estimates of summer temperature variation on annual to multi-century timescales. The late-twentieth century is not exceptionally warm in the new Tornetra¨sk record: On decadal-to-century timescales, periods around AD 750, 1000, 1400, and 1750 were all equally warm, or warmer. The warmest summers in this new reconstruction occur in a 200-year period centred on AD 1000. A ‘‘Medieval Warm Period’’ is supported by other paleoclimate evidence from northern Fennoscandia, although the new tree-ring evidence from Tornetra¨sk suggests that this period was much warmer than previously recognised. The paper is available under 'Open Access.' See also World Climate Report: ‘1500 Years of Cooling in the Arctic’

MoD Objects to Offshore Wind Farms as ‘A Threat to National Security’

By

Following on from the rumour that the plans for the siting 181 wind turbines on the Isle of Lewis are to be rejected due to environmental concerns, offshore wind farms have come under attack for the UK’s Ministry of Defence on the grounds that turbines interfere with its radar.

The story was reported in The Times newspaper: Wind farms ‘a threat to national security’

“The MoD has lodged last-minute objections to at least four onshore wind farms in the line of sight of its stations on the east coast because they make it impossible to spot aircraft, The Times has learnt. The same objections are likely to apply to wind turbines in the North Sea, part of the massive renewable energy project announced by John Hutton, the Energy Secretary, barely two months ago. They would be directly in line with the three principal radar defence stations, Brizlee Wood, Saxton Wold and Trimingham on the Northumberland, Yorkshire and Norfolk coasts.

Giving evidence to a planning inquiry last October, a senior MoD expert said that the turbines create a hole in radar coverage so that aircraft flying overhead are not detectable. In written evidence, Squadron Leader Chris Breedon said: “This obscuration occurs regardless of the height of the aircraft, of the radar and of the turbine.” He described the discovery as alarming.”

So it seems that whether wind farms are sited onshore or offshore, they will face strong objections.

Many thanks to readers who have donated to the upkeep of the blog using the ‘donate’ button.

Sea Ice Update

By

I have previously blogged about the record low (since satellite measurements began) for Arctic sea ice in 2007, and some of the contributory factors, here, here and here. The record high for sea ice coverage in the Antarctic received little or no media attention.

So what is the current situation? NASA’s earth observatory has an Arctic sea ice update here:

“After record retreat in September 2007, Arctic sea ice had been making a slow winter recovery. Mean sea ice extent remained at record-low levels in October 2007, but beginning in late October, sea ice grew by more than 150,000 square kilometers (about 58,000 square miles) per day for about 10 days—the fastest regrowth observed in the satellite record. Despite this rapid growth, sea ice extent remained below normal for November, though it was not a record low.”

According to the University of Illinois website The Cryosphere Today, sea ice coverage for January 31 2008 is about 900,000 square kilometers below average for the Arctic and about 500,000 square kilometers above average for the Antarctic. Compare past Arctic sea ice coverage from 1980 onwards with the present at the same time of the year here.

Don’t forget that blog readers can donate to the upkeep of this blog using the donate button on the right hand side. Many thanks to those who have already done so.