California’s coastal waters are getting more acidic. Fall-run chinook salmon populations in the Sacramento River are declining. Conifer forests on Sierra Nevada slopes are growing at higher elevations. That’s just a snapshot of how the California Environmental Protection Agency, summarizing studies looking back over several decades, says climate change is affecting the state’s natural resources.
John Christy, an atmospheric sciences professor at the University of Alabama at Huntsville, has a different view: He says the California EPA report “vastly overstates the impacts of greenhouse gases.” Average annual temperatures across the state have shown a slight increase over the past century, but he’s right that many questions remain about how recent trends compare with the climate centuries ago, before human activities had much impact on the environment.
The California EPA reports that butterflies in the Central Valley are emerging from hiding earlier in spring, glaciers in the Sierra Nevada have shrunk, and spring runoff from snowmelt has declined because of smaller snowpacks. Levels of carbon dioxide, methane, and other greenhouse gases in the state apparently increased between 1990 and 2011, but more recently decreased slightly because of industries and vehicles becoming more energy efficient.
Meanwhile, in southern Africa, the Namibian desert is getting even drier: One local police chief, Olani Imanul, said, “It has not rained for over two years here.” The drought in this arid corner of Africa may be the worst in three decades. Families are selling their livestock, eating less, and migrating to cities to find work. “An estimated 778,000 Namibians, a third of the population, are either severely or moderately food insecure,” UNICEF said in an online report.
Such effects emerge from the interplay of processes in the air, on land, and in the ocean that we still understand only partially. Weather extremes like droughts do not by themselves prove or disprove climate change, but long-term measurements show that climates, like our bodies, are fearfully and wonderfully made.