Climate Cast: Earth’s lungs inhaling less carbon

Think of the Amazon as earth's lungs.

The vast stands of thick rain forecast suck up carbon dioxide and store some of the extra carbon we humans have been belching into the atmosphere for a century.

This uptake of  atmospheric CO2 offsets more rapid climate change. But massive deforestation and changes in regional climate are making the Amazon a less effective carbon sink.

Join Kerri Miller and me Thursday at 9:45 am for Climate Cast on MPR News as we discuss how changes in the Amazon rain forecast may speed up climate changes in the coming decades.

Karl Mathiesen from the Guardian takes a closer look at how a study published in the journal Nature tracks changes in the ability of the Amazon to store atmospheric carbon.

The amount of carbon the Amazon’s remaining trees removed from the atmosphere fell by almost a third last decade, leading scientists to warn that manmade carbon emissions would need to be cut more deeply to tackle climate change.

Trees in untouched areas of the forest have been dying off across the basin at an increasing rate, found the study, published in Nature on Wednesday. Meanwhile the tree growth produced by higher CO2 levels in recent decades levelled off.

The authors said this may be because the Amazon’s seasonal weather variation had become more extreme. They also suggested more CO2 in the atmosphere was, counterintuitively, leading to trees dying younger.

Dr Roel Brienen of Leeds University said the Amazon was responsible for one-fifth to one-quarter of carbon sequestered on land, so any decline in its efficiency as a carbon sink was of consequence to efforts to combat climate change.

“If this trend continues then that is worrying because that means that basically the subsidies that we have been getting from nature – the forests that are taking up part of the emissions that we have been putting out into the atmosphere – if that is going to stop then that means that we have to make even stronger cuts in our CO2 emissions in order to keep the rate of climate change as low as possible,” he said.

More climate science news

Atlantic Ocean "conveyor belt" weakest in 1,000 years?

Cli-Fi, meet reality. Call it the "The Day After Tomorrow" scenario. Scientists have been concerned that a "freshening" of seawater in the North Atlantic from increased meltwater in Greenland could cause changes to critical ocean circulation patterns that can change weather and climates.

Now a new study in Nature Climate Change finds that changes in Atlantic Ocean currents are very likely already underway.

Possible changes in Atlantic meridional overturning circulation (AMOC) provide a key source of uncertainty regarding future climate change.

Maps of temperature trends over the twentieth century show a conspicuous region of cooling in the northern Atlantic. Here we present multiple lines of evidence suggesting that this cooling may be due to a reduction in the AMOC over the twentieth century and particularly after 1970. Since 1990 the AMOC seems to have partly recovered.

This time evolution is consistently suggested by an AMOC index based on sea surface temperatures, by the hemispheric temperature difference, by coral-based proxies and by oceanic measurements. We discuss a possible contribution of the melting of the Greenland Ice Sheet to the slowdown.

Using a multi-proxy temperature reconstruction for the AMOC index suggests that the AMOC weakness after 1975 is an unprecedented event in the past millennium (p > 0.99). Further melting of Greenland in the coming decades could contribute to further weakening of the AMOC.

Looking glass: Why record snows happen as climate changes

Record snowfall in Boston and big snowstorms in winter refute the notion of climate change right? Wrong. Here's a good explanation from the National Oceanic and Atmospheric Administration on why snowstorms can get bigger, even as climate gets warmer.

Are record snowstorms proof that global warming isn’t happening?

Wednesday, March 11, 2015

No. Snowstorms require two things: moisture and freezing air temperatures. There are plenty of places where winter temperatures would have to rise by 10, 20, even 30 degrees

Fahrenheit before it would stop snowing. Until then, snowstorms remain quite possible, and natural climate patterns and random variability will still lead to winters that are unusually cold and snowy in different locations.

One way to demonstrate that record snowstorms aren’t incompatible with a warmer climate is to look back at the historical record snowstorms and the seasonal conditions that spawned them.

An analysis of such storms between 1961-2010 showed that while most extreme snow storms did occur in seasons that were colder and wetter than average, about 35 percent of snow seasons that produced extreme snow events were warmer than average, and 30 percent were drier than average.

Summarizing that analysis as part of a “state of the science” review of climate change and extreme storms in 2014, a group of scientists concluded:

even if temperatures continue to warm as they have over the past several decades for the next few decades at least, then such record storms are possible, as they have been observed during otherwise warmer- and drier-than average seasons.

Not only are severe snowstorms possible in a warming climate, they may even be more likely. According to the Third National Climate Assessment, there is some evidence that cold season storms in the Northern Hemisphere have become both more frequent and more intense since 1950.

Extremely heavy snowstorms also increased in number during the last century in northern and eastern parts of the United States, although they have been less frequent since 2000.

Shifting climate hardiness zones

Winter hardy palm trees in Minnesota soon? Not likely. But climate zones continue to shift in the United States as extreme minimum winter temperature rise.

Here's more from NOAA on shifting climate plant hardiness zones.

Updated each decade, the U.S. Climate Normals from NOAA's National Climatic Data Center are 30-year averages of many pieces of weather information collected from thousands of weather stations nationwide.

Each time they are updated, an old decade is dropped, and a new one is added. The last update was in July 2011: the decade 1971-1980 was dropped, 2001-2010 was added, and the new 30-year window for the U.S. Climate Normals became 1981-2010.

Since the '70s was an unusually cool decade, while 2001-2010 was the warmest ever recorded, it is not surprising that the average temperature rose for most locations. For the United States as a whole, though, it was not daytime highs (maximum temperatures) but overnight lows (minimum temperatures) that rose the most compared with the 1970s.

Climate normals can help people understand what conditions they can expect wherever they may live… and plant. A previous article on Climate.gov explored the implications of the new climate normals for gardeners and landscapers.

Not only can plants can generally survive farther north than they used to, but the fire season is longer and pests are able to thrive and spread in forests and other natural landscapes. Pollination patterns may also be changing.