Spring Has Sprung... Earlier Than Ever

If you think spring has been arriving earlier, you’re right: although nothing has changed in Earth’s orbit, and the balance of day and night hours has not shifted, the warmth associated with spring has been tiptoeing in sooner than it did 40 years ago, Cornell University scientists reported in 2004 in the International Journal of Biometeorology (see also my June 4 column on how climate change is affecting airborne plant allergens). Models of climate change predict that the planet’s polar regions will feel the impact of a warmer world more than other regions, and an earlier spring, it now turns out, is no exception: in the arctic, winter is giving way to spring weeks earlier than it did just a decade ago, scientists report in Current Biology.

“Arctic environments are and will be exposed to the greatest warming,” says Toke T. Høye of the National Environmental Research Institute, University of Aarhus, Denmark, who led the research. “Our study confirms what many people already think, that the seasons are changing and it is not just one or two warm years but a strong trend seen over a decade.”

The scientists studied the timing of such signs of spring as when plants bloom, butterflies emerge and birds undergo seasonal migration. Most such studies had focused on seasonal shifts in temperate regions, finding that spring has advanced 2.5 days per decade for European plants and 5.1 days per decade for animals and plants globally over the last 40 or so years.

The arctic makes those regions looks like slackers when it comes to responding to global warming. Based on when six plant species flower and when three High Arctic bird species and 12 insects lay their eggs, they calculate that spring has advanced by over 30 days during the last decade for some events and an average of 14.5 days for all events that mark the season. “We were particularly surprised to see that the trends were so strong when considering that the entire summer is very short in the High Arctic—with just three to four months from snowmelt to freeze” at their study site in northeast Greenland, Høye said.

Is this reason to welcome or fear climate change? At this point, it’s hard to say. Spring definitely marks the awakening from winter hibernation and stasis for most arctic species. But the fact that different species are responding slightly differently to climate change could spell trouble: such variation, Høye said, could lead to problems by disrupting the complex web of species’ interactions. In temperate regions, for instance, migratory birds departing for the north earlier and earlier have already found that the food stocks they used to rely on along the way are not in sync with their new travel dates.