Tag Archives: climate change

Spring may come earlier to North American forests (Geophysical Research Letters)

By Catherine Zandonella, Office of the Dean for Research

Trees in the continental U.S. could send out new spring leaves up to 17 days earlier in the coming century than they did before global temperatures started to rise, according to a new study by Princeton University researchers. These climate-driven changes could lead to changes in the composition of northeastern forests and give a boost to their ability to take up carbon dioxide.

Trees play an important role in taking up carbon dioxide from the atmosphere, so researchers led by David Medvigy, assistant professor in Princeton’s department of geosciences, wanted to evaluate predictions of spring budburst — when deciduous trees push out new growth after months of winter dormancy — from models that predict how carbon emissions will impact global temperatures.

The date of budburst affects how much carbon dioxide is taken up each year, yet most climate models have used overly simplistic schemes for representing spring budburst, modeling for example a single species of tree to represent all the trees in a geographic region.

In 2012, the Princeton team published a new model that relied on warming temperatures and the waning number of cold days to predict spring budburst. The model, which was published in the Journal of Geophysical Research, proved accurate when compared to data on actual budburst in the northeastern United States.

In the current paper published online in Geophysical Research Letters, Medvigy and his colleagues tested the model against a broader set of observations collected by the USA National Phenology Network, a nation-wide tree ecology monitoring network consisting of federal agencies, educational institutions and citizen scientists. The team incorporated the 2012 model into predictions of future budburst based on four possible climate scenarios used in planning exercises by the Intergovernmental Panel on Climate Change.

The researchers included Su-Jong Jeong, a postdoctoral research associate in Geosciences, along with Elena Shevliakova, a senior climate modeler, and Sergey Malyshev, a professional specialist, both in the Department of Ecology and Evolutionary Biology and associated with the U.S. National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory.

The team estimated that, compared to the late 20th century, red maple budburst will occur 8 to 40 days earlier, depending on the part of the country, by the year 2100. They found that the northern parts of the United States will have more pronounced changes than the southern parts, with the largest changes occurring in Maine, New York, Michigan, and Wisconsin.

The researchers also evaluated how warming temperatures could affect the budburst date of different species of tree. They found that budburst shifted to earlier in the year in both early-budding trees such as common aspen (Populus tremuloides) and late-budding trees such as red maple (Acer rubrum), but that the effect was greater in the late-budding trees and that over time the differences in budding dates narrowed.

The researchers noted that early budburst may give deciduous trees, such as oaks and maples, a competitive advantage over evergreen trees such as pines and hemlocks. With deciduous trees growing for longer periods of the year, they may begin to outstrip growth of evergreens, leading to lasting changes in forest make-up.

The researchers further predicted that warming will trigger a speed-up of the spring “greenwave,” or budburst that moves from south to north across the continent during the spring.

The finding is also interesting from the standpoint of future changes in springtime weather, said Medvigy, because budburst causes an abrupt change in how quickly energy, water and pollutants are exchanged between the land and the atmosphere. Once the leaves come out, energy from the sun is increasingly used to evaporate water from the leaves rather than to heat up the surface. This can lead to changes in daily temperature ranges, surface humidity, streamflow, and even nutrient loss from ecosystems, according to Medvigy.

Read the abstract.

Citation:

Jeong, Su-Jong, David Medvigy, Elena Shevliakova, and Sergey Malyshev. 2013. Predicting changes in temperate forest budburst using continental-scale observations and models. Geophysical Research Letters. Article first published online: Jan. 25, 2013. DOI: 10.1029/2012GL054431

This research was supported by award NA08OAR4320752 from the National Oceanic and Atmospheric Administration, U.S. Department of Commerce.

Gypsy moth caterpillar takes bite out of forest carbon storage (Environmental Research Letters)

Forests are important carbon dioxide storage mechanisms, but a voracious leaf-eating caterpillar is cutting into the trees’ capacity to remove the greenhouse gas from the atmosphere, according to new research by scientists at Princeton University, Rutgers University and the United States Forest Service.

The gypsy moth caterpillar, widespread in the northeastern United States, can wreak devastation on forests as it devours the leaves of oak, pine, and other tree species. The new research found that this defoliation has a significant detrimental effect on the ecosystem’s capacity to act as a carbon sink.

The study found that an oak-pine forest in the New Jersey pinelands hit by the gypsy moth every five years would store about one-third less of the above-ground carbon as an unharmed similar forest, according to David Medvigy, assistant professor of geosciences at Princeton University.

The research was conducted by Medvigy and Karina Schäfer, assistant professor of ecosystem ecology at Rutgers University as well as researchers from the US Forest Service: Kenneth Clark of the Silas Little Experimental Forest in New Jersey and Nicholas Skowronski of the Northern Research Station in West Virginia.

The research was published in the journal Environmental Research Letters. (Read the open access article.) A news article about the study can be found here.

Citation: Medvigy, D., K. L. Clark, N. S. Skowronskiand and K. V. R. Schäfer. 2012. Simulated impacts of insect defoliation on forest carbon dynamics. Environ. Res. Lett. 7 045703

 

Truths we must tell ourselves to manage climate change (Vanderbilt Law Review)

Climate change is unwelcome news, and the best and worst outcomes consistent with current science are very different, says Princeton University’s Robert Socolow, professor of mechanical and aerospace engineering, in a new review article published in the Vanderbilt Law Review.  There are novel ways the environmental community, in its role as messenger, could tell the story about climate change using greater empathy and candor.  This essay, which was delivered as a keynote address at a symposium held Feb. 24, 2012 at the Vanderbilt Law School, addresses new ways to freshen the conversation.

The era of consciousness of climate change began in 1958 when Charles David Keeling began the first accurate measurements of carbon dioxide in the atmosphere. The seasonal oscillations were unexpected and the annual average has become a new index (the Keeling Curve) of global human impact.

Fifty-four years later, climate change negotiations in the United States and internationally are in paralysis. The current impasse has little social value and a “restart” button is needed. Such a button will be found when those already concerned about climate change become better at telling truths first to themselves and then to the general public. One can begin with acknowledgements that 1) climate change is unwelcome news, a challenge we would rather not have; and 2) the best and worst outcomes consistent with today’s climate change science are very different. Moreover, every nominal energy “solution” to climate change has a dark side and the solution’s proponents are not the ones to be counted upon to identify what can go wrong.

Accordingly, climate change is a problem of risk management requiring balancing the risks of disruption from climate change and the risks of disruption from mitigation and adaptation. Both public and private institutions need to find ways to overcome their reluctance to verify whether intended carbon reduction goals have actually occurred, so that progress can be accurately monitored and learning can occur. Individuals can be helped to become more aware of how their every-day activities create their carbon footprint. Population must reenter the conversation.

There are grounds for optimism. Science has discovered threats fairly early. Many helpful technologies are being developed and deployed. And, our moral compass is in working order, insisting that we care both for those alive today and for the collective future of our species.

Citation: Robert H. Socolow, “Truths We Must Tell Ourselves to Manage Climate Change.” Vanderbilt Law Review, Vol. 65, Number 6, pp. 1455-1478.

Read the full article: http://www.vanderbiltlawreview.org/content/articles/2012/11/Socolow_-65_Vand_L_Rev_1455.pdf

Changes in Greenland ice sheet over space and time (PNAS)

Polar ice sheets are melting and contributing to a global rise in sea-level. This study looked at changes in Greenland’s ice sheet from April 2002 to August 2011 and found that active areas of ice loss were concentrated on the southeastern and northwestern coasts, with ice mass in the center of Greenland steadily increasing over the decade.

Christopher Harig and Frederik J. Simons. Mapping Greenland’s mass loss in space and time. Proceedings of the National Academy of Sciences. Published online before print November 19, 2012, doi: 10.1073/pnas.1206785109

Read the abstract.

Twenty-first-century projections of North Atlantic tropical storms from CMIP5 models (Nature Climate Change)

Efforts to predict North Atlantic hurricane activity should focus on improving the ability of global climate models to capture the processes that control patterns of sea surface temperature change through better modeling of cloud physics, atmospheric convection, oceanic processes, the role of aerosols, and overall improvements in spatial resolution of the models, according to a new study by Gabriele Villarini, a postdoctoral research associate in the Department of Civil and Environmental Engineering at Princeton University, and Gabriel A. Vecchi, a scientist at the U.S. National Oceanic and Atmospheric Administration’s Geophysical Fluid Dynamics Laboratory in Princeton.

Villarini G. and Vecchi GA. Twenty-first-century projections of North Atlantic tropical storms from CMIP5 models, Nature Climate Change
Published online 13 May 2012

Read a summary of the paper (Geophysical Fluid Dynamic Laboratory)