Gail Taylor from the University of Southampton and colleagues studied the growth and leaf fall of Populus trees — a genus which includes aspen and poplars — growing in Tuscania and Wisconsin from 2003 to 2004. The trees were grown in plots under either current or elevated atmospheric carbon dioxide levels and their colour was monitored using remotely sensed images of canopy greenness. Leaves turned yellow later in the year under higher carbon dioxide concentrations, even when exposed to the same temperatures. The researchers think that the change in leaf colour is probably due to the effect of carbon dioxide on plant physiology.

Whereas earlier springtime leaf growth is strongly related to temperature, the belated autumn leaf fall — previously inexplicably — is not. Deciduous trees are staying greener for longer than they were 30 years ago owing to the earlier arrival of new leaves and later leaf falls.

In Science/Nature

The tropical belt has become wider in recent decades, with climate change the probable cause, research suggests.

“I am most concerned about species’ communities being torn apart,” says Stanford ecologist Terry Root. “It is all going to be quite a mishmash of things.”

The escalator effect

Emma Marris

Rising temperatures are changing mountain ecosystems as the heat forces some species upwards — until there is nowhere left to go. Emma Marris reports on the ‘escalator effect’, which is threatening species worldwide.

“We were quite shocked by how dramatic these changes have been,” says Wilson, who is now at the University of Exeter. “I feel very privileged to have seen those species and habitats while many of them are still here.”

The biological world is changing because of global warming. Most non-specialists are familiar with poleward shifts — migration routes and species distributions that are creeping north in the Northern Hemisphere and south in the Southern Hemisphere as the equator-facing edges of these historic ranges become too hot for species to handle.

The same phenomenon is happening in three dimensions, though there is less data and less media coverage for these upward trends. As the climate warms, there is a corresponding increase in temperature at any given elevation. And any species unable to take the heat — or related changes in, for example, precipitation — will generally move up the mountain towards colder climes, until they reach the top.

The Harper government is opening the door to “wide-ranging” and “large scale” impacts to the earth’s ecosystems because of its refusal to recognize a tipping point in the battle against global warming as it heads into major United Nations climate change summit that begins on Monday, warns a newly-released federal document.

Foreign Affairs officials who prepared the internal research paper suggested that the government could improve its environmental policies if it recognized the dangers associated with allowing human activity to contribute to warming the planet’s average temperature by more than two degrees Celsius.

“The scientific uncertainty surrounding the temperature increase thresholds that would trigger global scale impacts (i.e., slowing of the North Atlantic Ocean currents, collapse of Greenland and/or West Antarctic ice sheets), highlights the merits of a precautionary approach,” reads the document that was released to the Pembina Institute following an access to information request. “Some recent studies suggest that these wide-reaching, large-scale impacts could be triggered by a temperature increase as low as one degree Celsius (to) two degrees Celsius from pre-industrial levels.”

Fertilizing the ocean with iron or other nutrients to cause large algal blooms, has been proposed as a possible solution to global warming because the growing algae absorb carbon dioxide but research performed at Stanford and Oregon State Universities and published in the Journal of Geophysical Research suggests that ocean fertilization may not be an effective method of reducing carbon dioxide in the atmosphere.

Only when the people realised that the “selfish plundering wastrel bastards up in the future” were doing the same thing to their era were aorist rods banned. “They claimed it was for the sake of their grandparents and grandchildren, but it was of course for the sake of their grandparent’s grandchildren, and their grandchildren’s grandparents.”

10 April 2007

Jim Hansen
Introduction. “Animals are on the run. Plants are migrating too.” When I wrote those words in 20061, I was trying to draw attention to the fact that climate change is underway. People do not notice climate change readily, because it is masked by large day-to-day weather fluctuations, and we reside in comfortable homes and offices.