Climate impacts report gives US a wake-up call

Global warming could destroy some of North America's most precious ecosystems, according to the first scientific assessment of the potential consequences of global warming on the US. Science and environmental groups have welcomed the report, but say it should be viewed as a warning to begin reducing greenhouse gas (ghg) emissions.

The assessment says that places like Florida’s coral reefs and the alpine meadows of the Rocky Mountains are most vulnerable to the harmful effects of climate change. Such ecosystems are threatened by their limited capacity to adapt to climatic changes and already existing stresses from air and water pollution, habitat fragmentation, and overuse.

“The assessment shows that many of the country’s distinct natural features could deteriorate as a result of changing climate,” said Dr. Susan Subak, a senior research associate at the Natural Resources Defense Council (NRDC). “Whether we’re talking about fisheries and recreational areas on the coasts, or the habitats of America’s mountains and deserts, rising temperatures will put further stress on our natural areas.”

The report, National Assessment of Potential Impacts of Climate Variability and Change which was compiled over three years by the US Global Change Research Program, covers all regions of the US and assesses the potential impacts of climate variability and change on water, agriculture, human health, forests, coastal areas, and marine resources.

The report is a snapshot of the current state of knowledge produced through a series of regional and sectoral assessments. The report release was preceded by a multistage peer-review process involving more than 300 scientific and technical experts throughout the US.

The report focuses exclusively on the potential impacts of global warming, given selected climate change scenarios. It identifies regions and sectors most vulnerable to climate change, opportunities to adapt to likely changes, and the most critical information needs for the US to be better positioned to predict climate change impacts.

“No matter how aggressively emissions are reduced, the world will still experience some climate change,” the report states. This is because elevated concentrations of ghgs will remain in the atmosphere for decades as the climate system responds only slowly to changes in human inputs.

Although the report’s publication has been welcomed by environmentalists, they say that it represents a wake up call to the US. “This report brings the meaning of global climate change home to every American,” said Dr. Susanne Moser of the Union of Concerned Scientists. “Even if the impacts ultimately manifest differently from what the report projects, everyone will experience some changes, and everyone should know that climate change is not science fiction. In some regions, like Alaska, the impacts of warming are here, now.”

Among the key findings of the report are:

  • ecosystems are highly vulnerable to the projected rate and magnitude of climate change. The goods and services lost through the disappearance or fragmentation of certain ecosystems are likely to be costly or impossible to replace, the assessment claims
  • according to the climate models used in the assessments, temperatures will rise 5-10° F (2.7 – 5.5°C) on average in the next 100 years if trends in ghg emissions continue, but increases will vary somewhat from one US region to the next. It is also very likely that more rain will come in heavy downpours, increasing the risk of floods
  • throughout the US, water is likely to become one of the key concerns in coming decades: droughts, floods, declining snow packs and water quality and possibly greater water use conflicts could become even more common problems than they are today
  • climate change and the resulting rise in sea level are likely to worsen threats to buildings, roads, powerlines and other infrastructure along the coast. The report also claims sea-level rise will probably cause the loss of some barrier beaches, islands, and wetlands and worsen storm surges and flooding during storms
  • overall, US crop productivity is likely to increase over the next few decades, but the gains will not be uniform across the US. Falling prices and competition are likely to cause problems for some farmers. And pests, droughts and floods could reduce some of the benefits from higher temperatures, precipitation and carbon dioxide
  • similarly, forest productivity is likely to increase in some areas over the next few decades, but fires, insects, droughts and diseases will possibly decrease productivity. Climate change will cause long-term shifts in forest species, such as sugar maples moving north out of the Northeast or economically important soft wood species moving from the Southeast to the Mid-Atlantic

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