Science News

Spring forward?

Wed, 2nd May 2012

Louise Anthony

Global warming could make Spring arrive even earlier than scientists have predicted.

NarcissusIn warmer weather, plants produce their first leaves and flower earlier in the year.  In order to predict the effect global warming may have on this, plant scientists have carried out experiments in which they warm a small area over several years and record the advance in flowering and leafing dates.

We use small-scale warming experiments to predict future changes, lead author Dr. Elizabeth Wolkovich says.  We wanted to look at this assumption we have that these experiments will give us similar answers to long-term records.

But by analysing the results of many of these experiments alongside data from long-term observational studies, in a study called a meta-analysis, scientists from the National Centre for Ecological Analysis and Synthesis have shown that this could significantly underestimate the effect.  Long-term observational studies report the advance in flowering and leafing to be up to eight fold larger than warming experiments have demonstrated.

If we look at long-term records, we see that for every degree celsius of warming, we find five to six days advance in plant leafing and flowering.  For the experiments, its something like half a day to one-and-a-half days at most, Dr. Wolkovich explains.

As plants form the basis of many ecosystems and food webs, the date at which they produce leaves and flowers has a huge impact upon the local ecology.  In addition, flowering and leafing dates affect the uptake of carbon dioxide by plants, as well as the nitrogen cycle and even the water supply.  The problem is that for much of the world, we lack long-term records and so are completely reliant on predictions made from these warming experiments - and this could be leading us to dramatically under-predict the future effects of climate change.

There is some good news, too.  Dr. Wolkovich believes that warming experiments currently underway are better designed, and can give a more accurate picture of the effects of global warming.  More and more studies are also looking at other factors associated with global warming - such as changes in rainfall.  But its important that we carry on with the long-term studies alongside this.

I think we really need to go after what caused this discrepancy.  It could be that short-term experiments are only going to get us part of the way towards what were seeing in the long term, and something else is going on in the long-term data, Dr. Wolkovich cautions.


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At least here in Belgium we don't have seasons anymore. In 2011 we had summer days that were colder than some winterdays. Spring was summer, summer was autumn, autumn was like spring again, and winter was like autumn again. Nizzle, Mon, 7th May 2012

Earlier planting seasons sound like a good thing for agriculture.
Although, perhaps there would be the risk of more early spring temperature & rainfall variability, so that planting would still be hampered somewhat.

Some of the best agriculture in the USA are in the irrigated, very hot regions (otherwise desert).

It has been noted in the Arctic that the maximum sea ice extent has been getting later in the year.

I do wonder if this later maximum sea ice extent is due to ice still forming in regions that otherwise would be thickening in the winter, while more southerly regions would otherwise have started to melt had the sea ice extent been greater.

One has to keep in mind that all the global warming in the world does not affect the length of day at any particular latitude (which is important both for sea ice as well as planting). CliffordK, Mon, 7th May 2012

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