Topic: Energy and Environment

Greener, Not Browner

A recent Science paper by J-F. Busteri and 30 named coauthors assisted by 239 volunteers found, looking at global drylands (about 40% of land areas fall into this category), that we had undercounted global forest cover by a whopping “at least 9%.” 239 people were required to examine over 210,000 0.5 hectare (1.2 acre) sample plots in GoogleEarth, and classify the cover as open or forested. Here’s the resultant cool map:

This has been the subject of a flood of recent stories, blog posts, tweets, and whatever concerning Bastin et al. But here at the Center for the Study of Science, we’re value added, so here’s some added value.

Last year, Zaichin Zhu and 31 coauthors published a remarkable analysis of global vegetation change since satellite sensors became operational in the late 1970s. The vast majority of the globe’s vegetated area shows greening, with 25-50% of that area showing a statistically significant change, while only 4% of the vegetated area is significantly browning. Here’s the mind-boggling map:

Trends in Leaf Area Index, 1978-2009. Positive tones are greening, negative are browning, and the dots delineate where the changes are statistically significant. There is approximately 9 times more area significantly greening up than browning down.

Trends in Leaf Area Index, 1978-2009. Positive tones are greening, negative are browning, and the dots delineate where the changes are statistically significant. There is approximately 9 times more area significantly greening up than browning down. 

Hope you’re sitting down for the money quote:

We show a persistent and widespread increase of growing season integrated LAI (greening) over 25% to 50% of the global vegetated area, whereas less than 4% of the globe shows decreasing LAI (browning). Factorial simulations with multiple global ecosystem models show that CO2 fertilization effects explain 70% of the observed greening trend…

And the other greening driver that stood out from the statistical noise was—you guessed it—climate change.

Now, just for fun, toggle back and forth between the two maps. As you can see, virtually every place where there’s newly detected forest is greening, and a large number of these are doing it in a statistically significant fashion. This may lead to a remarkable hypothesis—that one of the reasons the forested regions were undercounted in previous surveys (among other reasons) is that there wasn’t enough vegetation present to meet Bastin’s criterion for “forest,” which is greater than 10% tree cover, and carbon dioxide and global warming changed that.

References:

Bastin, F-L., et al., 2017. The extent of forest in dryland biomes. Science 356, 635-638.

Zhu, Z., et al., 2016. Greening of the earth and its drivers. Nature Climate Change, DOI: 10.1038/

NCLIMATE30004. 

Global Science Report: Sea Ice Expansion in the Southern Hemisphere Is Real and Driven by Falling Temperatures

While there’s been thousands of legacy media stories about the very real decline in summer sea-ice extent in the Arctic Ocean, we can’t find one about the statistically significant increase in Antarctic sea ice that has been observed at the same time.

Also, comparisons between forecast temperature trends down there and what’s been observed are also very few and far between. Here’s one published in 2015:

Observed (blue) and model-forecast (red) Antarctic sea-ice extent published by Shu et al. (2015) shows a large and growing discrepancy, but for unknown reasons, their illustration ends in 2005.

Observed (blue) and model-forecast (red) Antarctic sea-ice extent published by Shu et al. (2015) shows a large and growing discrepancy, but for unknown reasons, their illustration ends in 2005.

For those who utilize and trust in the scientific method, forming policy (especially multi-trillion dollar policies!) on the basis of what could or might happen in the future seems imprudent. Sound policy, in contrast, is best formulated when it is based upon repeated and verifiable observations that are consistent with the projections of climate models. As shown above, this does not appear to be the case with the vast ice field that surrounds Antarctica.

According to the most recent report by the Intergovernmental Panel on Climate Change (IPCC), CO2-induced global warming will result in a considerable reduction in sea ice extent in the Southern Hemisphere. Specifically, the report predicts a multi-model average decrease of between 16 and 67 percent in the summer and 8 to 30 percent in the winter by the end of the century (IPCC, 2013). Given the fact that atmospheric CO2 concentrations have increased by 20 percent over the past four decades, evidence of sea ice decline should be evident in the observational data if such model predictions are correct. But are they?

Thanks to a recent paper in the Journal of Climate by Josefino Comiso and colleagues, we now know what’s driving the increase in sea-ice down there. It’s—wait for it—cooling temperatures over the ocean surrounding Antarctica.

Will Warming and “Acidification” Create Chaos in Coastal Ecosystems?

One of the key concerns about climate change is ecosystem resilience. This is particularly true for those that are anchored over large locations with little ability to move. Ecological communities in the Chesapeake Bay come to mind.

According to the U.S. National Climate Assessment report published in 2014 (Melillo et al., 2014), there is “very high confidence that coastal ecosystems are particularly vulnerable to climate change because they have already been dramatically altered by human stresses, as documented in extensive and conclusive evidence” (Moser et al., 2014). Additionally, the report claims there is “very high confidence that climate change will result in further reduction or loss of the services that these ecosystems provide, as there is extensive and conclusive evidence related to this vulnerability” (Moser et al., 2014).

That Assessment has been criticized as being far too alarmist, too political, and very incomplete with regard to its summarization of important scientific literature. It didn’t help that when it was released, the National Oceanic and Atmospheric Administration (whose bailiwick includes coastal ecosystems), called the report “a key deliverable in President Obama’s Climate Action Plan” in the press release for its rollout.

It’s important to quantify claims like the ones made above, and one type of ecosystem that has received considerable attention in this regard is the seagrass biome. These dense underwater meadows are found in numerous coastal waters, including those of the United States. They are a foundational basis for an ecosystem as diverse and variegated as those associated with coral reefs, but they get little public attention because they aren’t nearly as showy. But they are important. Their presence helps to reduce coastal erosion, improve water quality and mediate ocean chemistry, as which adds economic value. Given the important functions that they perform within their coastal ecosystems, it should come as no surprise, therefore, that concerns have arisen over the current and future ability of seagrass ecosystems to withstand rising atmospheric CO2 concentrations – i.e. global warming and ocean acidification.

Giving Nature’s “Hiatus” Paper a Closer Read

There’s been a small gaggle of news stories about a new paper by Iselin Medhaug and colleagues in the May 4 issue of Nature that concludes that climate models are just fine and their sensitivity to carbon dioxide is spot-on.

If one adjusts the data observed during the balance of the “hiatus” in warming, by filling in hot data where there was none, and adjust the model predictions downward that would be the likely result. I’ve gone through the Abstract line-by-line, so you can see these papers the way a climate scientist might.

Between 1998 and 2012,

Actually, the pause was between 1997 and 2014, as shown in even the warm-revised data from the Climate Research Unit from the University of East Anglia:

a time that coincided with political negotiations for preventing climate change,

It appears as though this was put in to signal they have no problem mixing politics with science. They are obviously signaling that the 1998-2012 “hiatus” (well, actually, 1997-2014) isn’t a good excuse for Donald Trump to walk away from the Paris Agreement, which does nothing measurable to stop climate change in the 21st century.

What The Economist Didn’t Tell You about Greenland’s Ice

At the contentious interface of climate science and policy, there’s one thing that people of all flavors agree upon: if Greenland were to shed all its ice in a century that would be an unmitigated catastrophe, raising sea levels an average of 22 feet simply from the sheer volume of water contained thereon.

It therefore stands to reason that a melting Greenland makes for good copy, and The Economist’s witty scribes have just published two alarming articles (here and here). Alarming, that is, because they left out a few pertinent facts.

“The most worrying changes are happening in Greenland, which lost an average of 375bn tonnes of ice per year between 2011 and 2014.”

This is a finely selected cherry that The Economist plucked. 2012 was an exceedingly warm year averaged over the island-continent. Had they included all the recent data, they would have shown that the surface mass balance budget of ice on Greenland recently reached a record high compared to the previous three decade. This is simply the accumulation of ice and snow minus losses from melting and and sublimation (the direct evaporation of snow), and you can see how unusual 2012 was in the figure below. The net ice loss is the accumulation minus the calving of glaciers, which, according to the Danish Meteorological institute (DMI) is about 200 gigatonnes (billion metric tons) per year. 

Source:  Danish Meteorological Institute

“This is equivalent of over 400 massive icebergs measuring 1km on each side disappearing each year.”

At the turn of this century, the U.S. Geological Survey reported the volume of Greenland’s ice at 2,600,000km3. The maximum melt of 400km3 is a grand total of 1/5000th of its ice.

The United Nations’ Intergovernmental Panel on Climate Change (IPCC) projects that melting of Greenland’s ice will raise sea level a bit under one-tenth of a meter, or three inches by 2100. 

“Even if current emissions remain stable, the consensus is that global sea levels will rise 74cm [29 in] by the end of the century.”

Nope. The same IPCC science summary projects around 38cm [15in] for this scenario.

With regard to the much-feared sudden loss of Greenland’s ice, we read that “little is known about how Greenland’s vast ice sheet will react to future warming.”

Well, when it comes to the big one, no, not really. A 2013 ice core got all the way back to the beginning of the previous interglacial, when there was a 6,000 year period of very warm summer temperatures. Prior to this work by Dorthe Dahl-Jensen and her colleagues, it was thought summer temperatures in this period, called the Eemian, were about 2⁰C warmer than the 20th century average over northwest Greenland, where the core was drilled. 

Instead, Dahl-Jensen found that it averaged a whopping 6⁰ warmer. She estimated this was associated with a maximum loss of about 30% of Greenland’s ice. That may be charitable because where she drilled, in the cold northwestern region, the ice core revealed that the thickness of the ice was reduced by about 10%. Another, more recent study also found 6⁰C of warming, this time at Summit, where Greenland’s ice cap reaches maximum elevation. That work did not use the ice itself to estimate the Eemian altitude, but a computer model, which showed around a 70% loss of total Greenland ice.

So this much heat rained down on Greenland during the Eemian: 6⁰C X 6,000 summers, or 36,000 degree-summers. And let’s say, maybe, humans could warm it 5⁰C for 500 summers, or 2,500 degree-summers. That would only knock 2500/36000 of the maximum 30% of the ice off, or two percent. This works out to five inches of sea-level rise from the melting of Greenland in the first study and 13 in the second one. 

Most Economist readers aren’t aware of the true nature of the literature on Greenland’s ice and don’t have a friendly climatologist to supply them the important links The Economist didn’t. No wonder so many are worried. 

Global Science Report: Antarctic Updates

The northern end of the Antarctic Peninsula is Warming Fast
BBC, August 23, 2012

No, it’s not. When BBC reported this, the Northern Peninsula hadn’t on average warmed a lick in thirty years.

In the 1990s and early part of this century, news reports about the dramatic warming of the northernmost Antarctic Peninsula—the tip of the 800-mile dagger pointed at the heart of Tierra del Fuego—were a common staple. And, while scientists wouldn’t write this in the literature, they were happy to blame it on dreaded carbon dioxide on television, as paleoclimatologist Robert Mulvaney did in the 2012 BBC feature.

The story has become increasingly curious. Marc Oliva of the University of Lisbon recently examined the high quality weather stations over the northern peninsula and the nearby South Shetland Islands. There is a decent warming trend, averaging around 1.5⁰C, from the beginning of the data in 1957 (the year when Antarctica was instrumented as a part of the International Geophysical Year) to the early 1980s, or about a quarter-century. That’s a warming, if it continued (and surely it would!), of 6⁰C per century. The warming that gets huge attention is actually only from a single station, Faraday (now renamed Vernadsky), which warmed roughly 2.5⁰C during the same period. If that continued (and surely it would!), that’s 10⁰C/century!

Oliva et al. wrote that the “Faraday/Vernadsky warming trend is an extreme case, circa twice those of the long-term records from other parts of the AP.” The variability in the Faraday/Vernadsky record is also huge—around three times as much as other stations in the area, probably because it is often at the edge of the sea-ice.

A Climate of Science Deception

Former Energy Department Undersecretary Steven Koonin caused quite a stir yesterday in an interview with Mary Kissel of The Wall Street Journal when he stated Federal scientists purposefully misled the public about climate change. He recounted that the 2014 National Assessment of Climate Change Impacts in the United States emphasized a dramatic increase in Atlantic hurricane power beginning in 1980. However, this conveniently chosen segment of the historical record does not tell the entire story—the narrative that hurricanes are right now getting more frequent and intense due to climate change just does not stand up to scrutiny.

The offending figure is on Page 42 of the document (reproduced here). It is in Chapter 2 of the report, which is called “Our Changing Climate.”

These are graphs of something called the Power Dissipation Index (PDI) for Atlantic and Eastern North Pacific hurricanes. Note that the data begins in 1970 and ends in 2009. The text explains the beginning date by saying “there is considerable uncertainty in the record prior to the satellite era (early 1970s).”

This is true, but phenomenally disingenuous. Another hurricane scientist, conspicuously absent from the author list, is Chris Landsea of the National Hurricane Center, who developed the Center’s historical hurricane archive, known as HURDAT2. According to Landsea, the problem in the early record (which should be obvious) is that some storms will be missed, not the other way around! In his words, in a 2013 article in Monthly Weather Review, “Some storms were missed, and many intensities are too low in the pre-aircraft reconnaissance era (before 1944 in the western half of the basin) and in the pre-satellite era (before 1972 for the entire basin).

Therefore, prior to 1972, any history is likely to underestimate the PDI rather than overestimate it.