Tag: carbon emissions

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. 

How Does One Justify One of the Most Expensive Regulations in American History?

In an effort to justify its massive global warming regulations, the Obama Administration had to estimate how much global warming would cost, and therefore how much money their plans would “save.” This is called the “social cost of carbon” (SCC). Calculating the SCC requires knowledge of how much it will warm as well as the net effects of that warming. Needless to say, the more it warms, the more it costs, justifying the greatest regulations. 

Obviously this is a gargantuan task requiring expertise a large number of agencies and cabinet departments. Consequently, the Administration cobbled a large “Interagency Working Group” (IWG) that ran three combination climate and economic models. A reliable cost estimate requires a confident understanding of both future climate and economic conditions. The Obama Administration decided it could calculate this to the year 2300, a complete fantasy when it comes to the way the world produces and consumes energy. It’s an easy demonstration that we have a hard enough time getting the next 15 years right, let alone the next 300.

Consider the case of domestic natural gas. In 2001, everyone knew that we were running out. A person who opined that we actually would soon be able to exploit hundreds of years’ worth, simply by smashing rocks underlying vast areas of the country, would have been laughed out of polite company. But the previous Administration thought it could tell us the energy technology of 2300. As a thought experiment, could anyone in 1717 foresee cars (maybe), nuclear fission (nope), or the internet (never)? 

On the climate side alone, there’s obviously some range of expected warming, often expressed as the probabilities surrounding some “equilibrium climate sensitivity” (ECS), or the mean amount of warming ultimately predicted for a doubling of atmospheric carbon dioxide. In the UN’s last (2013) climate compendium, their 100+ computer runs calculated an average of 3.2°C (5.8°F). A rough rule of thumb would be that this is also an estimate of the total temperature change predicted from the late 20th century to the year 2100.

You Ought to Have a Look: On Fixing Science

You Ought to Have a Look is a regular feature from the Center for the Study of Science. While this section will feature all of the areas of interest that we are emphasizing, the prominence of the climate issue is driving a tremendous amount of web traffic. Here we post a few of the best in recent days, along with our color commentary.

This week we focus on an in-depth article in Slate authored by Sam Apple that profiles John Arnold, “one of the least known billionaires in the U.S.” Turns out Mr. Arnold is very interested in “fixing” science. His foundation, the Arnold Foundation, has provided a good deal of funding to various research efforts across the country and across disciplines aimed at investigating how the scientific incentive structure results in biased (aka “bad”) science. His foundation has supported several high-profile science-finding replication efforts, such as those being run by Stanford’s John Ioannidis (whose work we are very fond of) and University of Virginia’s Brian Nosek who runs a venture called the “Reproducibility Project” (and who pioneered the badge system of rewards for open science that we previously discussed). The Arnold Foundation has also provided support for the re-examining of nutritional science, an effort lead by Gary Taubes (also a favorite of ours), as well as investigations into the scientific review process behind the U.S. government’s dietary guidelines, spearheaded by journalist Nina Teicholz.

Apple writes that:

In my conversations with Arnold and his grantees, the word incentives seems to come up more than any other. The problem, they claim, isn’t that scientists don’t want to do the right thing. On the contrary, Arnold says he believes that most researchers go into their work with the best of intentions, only to be led astray by a system that rewards the wrong behaviors.

This is something that we, too, repeatedly highlight at the Center for the Study of Science and investigating its impact is what we are built around.

Apple continues:

[S]cience, itself, through its systems of publication, funding, and advancement—had become biased toward generating a certain kind of finding: novel, attention grabbing, but ultimately unreliable…

“As a general rule, the incentives related to quantitative research are very different in the social sciences and in financial practice,” says James Owen Weatherall, author of The Physics of Wall Street. “In the sciences, one is mostly incentivized to publish journal articles, and especially to publish the sorts of attention-grabbing and controversial articles that get widely cited and picked up by the popular media. The articles have to appear methodologically sound, but this is generally a lower standard than being completely convincing. In finance, meanwhile, at least when one is trading with one’s own money, there are strong incentives to work to that stronger standard. One is literally betting on one’s research.”

A CO2-Induced Increase in Subtropical North Atlantic Coccolithophore Abundance

Coccolithophores are calcifying phytoplankton that comprise the base of marine food webs all across the world ocean. They play an important role in the cycling of carbon into the deep ocean and act as a feedback to climate change. Anything that alters their function or abundance, therefore, could have significant impacts on marine ecosystems and global climate. Thus, it is no surprise that scientists are interested in how coccolithophores will respond to future changes in atmospheric CO2 and climate. And in this regard, Krumhardt et al. (2016) say there has been “much speculation [that has] inspired numerous laboratory and mesocosm experiments, but how they are currently responding in situ is less well documented.” Working to provide just such an in situ analysis, the team of four researchers thus set out to analyze coccolithophore abundance in the subtropical North Atlantic over the period 1990 to 2014.

To accomplish their objective, Krumhardt et al. used coccolithophore pigment data collected at the Bermuda Atlantic Time-series Study (BATS) site (located at 31.7°N, 64.2°W in the Sargasso Sea) in conjunction with satellite estimates of surface chlorophyll and particulate inorganic carbon as a proxy measure of coccolithophore abundance. Results of their analysis revealed that “coccolithophore populations in the North Atlantic subtropical gyre have been increasing significantly over the past two decades. More specifically, they note there was a 37 percent increase in euphotic zone-integrated (integrated from 140 m depth) in coccolithophore pigment abundance at BATS and a larger 68 percent increase in the upper 30 m of the water column (see figure below). Such findings, in the words of the authors, add to those of a growing number of studies showing that coccolithophores in the North Atlantic “are increasing in abundance and are likely stimulated by additional carbon from anthropogenic sources.”

Elevated CO2 Stimulates the Growth of Papaya

Papayas are spherical or pear-shaped fruits known for their delicious taste and sunlit color of the tropics. Upon his arrival to the New World, Christopher Columbus apparently could not get enough of this exotic fruit, reportedly referring to it as the “the fruit of angels.” And the fruit of angels it may indeed be, as modern science has confirmed its value as a rich source of important vitamins, antioxidants and other health-promoting substances to the consumer.

Papaya production has increased significantly over the past few years to the point that it is now ranked fourth in total tropical fruit production after bananas, oranges and mango. It is an important export in many developing countries and provides a livelihood for thousands of people. It should come as no surprise, therefore, that scientists have become interested in how this important food crop might respond to increasing levels of atmospheric CO2 that are predicted for the future.

Such interest was the focus of a recent paper published in the scientific journal Scientia Horticulturae by Cruz et al. (2016). Therein, the team of five researchers examined “the effect of the elevated CO2 levels and its interaction with Nitrogen (N) on the growth, gas exchange, and N use efficiency (NUE) of papaya seedlings,” as they note there are no publications examining such for this species to date. To accomplish their objective, Cruz et al. grew Tainung #1 F1 Hybrid papaya seeds in 3.5 L plastic pots in a climate-controlled greenhouse at the USDA-ARS Crops Research Laboratory in Fort Collins, Colorado under two different CO2 concentrations (390 or 750 parts per million) and two separate N levels (8 mM NO3- or 3 mM NO3-). CO2 fumigation was performed for only 12 hours per day (during the day, 06:00 h to 18:00 h) and N treatments were applied to the pots weekly as a nutrient solution to reach the desired N levels. The experiment concluded 62 days after treatment initiation.

In discussing their findings, Cruz et al. report that compared to ambient levels of CO2, elevated CO2 increased photosynthesis by 24 and 31 percent in the low and high N treatments, respectively. Plant height, stem diameter and leaf area in the high N treatment were also enhanced by 15.4, 14.0 and 26.8 percent, respectively, and by similar amounts for the height and stem diameter in the low N treatment. Elevated CO2 also increased the biomass of leaf, stem plus petiole, and root dry mass of papaya plants regardless of N treatment, leading to total dry mass enhancements of 56.6 percent in the high N treatments and 64.1 percent in the low N treatments (see figure below).

Figure 1. Total dry mass of papaya plants grown in controlled chambers at two different CO2 concentrations (High and Low; 750 and 390 ppm) and two different N treatments (High and Low; 8 mM NO3- or 3 mM NO3-). Adapted from Cruz et al. (2016).

Figure 1. Total dry mass of papaya plants grown in controlled chambers at two different CO2 concentrations (High and Low; 750 and 390 ppm) and two different N treatments (High and Low; 8 mM NO3- or 3 mM NO3-). Adapted from Cruz et al. (2016).

 

Cruz et al. also report that “significant, but minor, differences were observed in total N content (leaf plus stem + petiole plus roots) between plants grown at different CO2 concentrations, but the same N levels.” Consequently, plant Nitrogen Use Efficiency (NUE) – the amount of carbon fixed per N unit – was around 40 percent greater in the CO2-enriched environments, regardless of the N level in the soil.

Commenting on their findings, Cruz et al. write that contrary to some other studies, which have suggested that low N reduces plant responses to increased CO2 levels, they found no such decline. In fact, their data indicate that elevated CO2 “alleviated the effect of low N on dry matter accumulation in papaya,” which they surmised is at least partially explained by a larger leaf area and higher rate of photosynthesis per leaf area unit observed under elevated CO2.

In light of all of the above, Cruz et al. conclude that “an increase in the atmospheric CO2 concentration [is] beneficial for dry mass production of papaya and alleviate[s] the negative effects of N reduction in the substrate on papaya growth.” Thus, in the future, those who cultivate this fruit of angels should find an angel in the ongoing rise in atmospheric CO2.

 

Reference

Cruz, J.L., Alves, A.A.C., LeCain, D.R., Ellis, D.D. and Morgan, J.A. 2016. Interactive effects between nitrogen fertilization and elevated CO2 on growth and gas exchange of papaya seedlings. Scientia Horticulturae 202: 32-40.

Elevated CO2: A Key Driver of Global Greening Observations

Despite a constant barrage of stories portraying rising atmospheric carbon dioxide (CO2) as a danger and threat to the planet, more and more scientific evidence is accruing showing that the opposite is true. The latest is in a paper recently published in the journal Scientific Reports, where Lu et al. (2016) investigated the role of atmospheric CO2 in causing the satellite-observed vegetative greening of the planet that has been observed since their launch in 1978.

It has long been known that rising CO2 boosts plant productivity and growth, and it is equally well-established that increased levels of atmospheric CO2 reduce plant water needs/requirements, thereby improving their water use efficiency. In consequence of these two benefits, Lu et al. hypothesized that rising atmospheric CO2 is playing a significant role in the observed greening, especially in moisture-limited areas where soil water content is a limiting factor in vegetative growth and function. To test their hypothesis, the three scientists conducted a meta-analysis that included 1705 field measurements from 21 distinct sites from which they evaluated the effects of atmospheric CO2 enrichment on soil water content in both dryland and non-dryland systems.

A Century of Precipitation Trends in Victoria, Australia

In the debate over CO2-induced global warming, projected impacts on various weather and climate-related phenomena can only be adjudicated with observed data. Even before the specter of dreaded global warming arose, scientists studied historical databases looking for secular changes or stability. With the advent of general circulation climate models, using historical data, scientists can determine whether any observed changes are consistent with the predictions of these models as atmospheric carbon dioxide increases. An example of the pitfalls in such work was recently presented by Rahmat et al. (2015), who set out to analyze precipitation trends over the past century at five locations in Victoria, Australia. More specifically, the authors subjected each data set to a series of statistical tests to “analyze the temporal changes in historic rainfall variability at a given location and to gain insight into the importance of the length of data record” on the outcome of those tests. And what did their analyses reveal?

When examining the rainfall data over the period 1949-2011 it was found that all series had a decreasing trend (toward less rainfall), though the trends were significant for only two of the five stations. Such negative trends, however, were reversed to positive in three of the five stations when the trend analyses were expanded over a longer time domain that encompassed the whole of the 20th century (1900-2011 for four stations and 1909-2011 for the fifth one). In addition, the two stations with statistically significant negative trends during the shorter time period were also affected by the longer analysis. Though their trends remained negative, they were no longer statistically significant when calculated over the expanded 112 years of analysis. In summation, in the expanded analysis the “annual rainfall time series showed no significant trends for any of the five stations.”

In light of the above findings, Rahmat et al. write that “conclusions drawn from this paper point to the importance of selecting the time series data length in identifying trends and abrupt changes,” adding that due to climate variability, “trend testing results might be biased and strongly dependent on the data period selected.” Indeed they can be; and this analysis shows the absolute importance of evaluating climate model projections using data sets that have been in existence for sufficiently long periods of time (century-long or more) that are capable of capturing the variability of climate that occurs naturally. And when such data sets are used, as in the case of the study examined here, it appears that the modern rise in CO2 has had no measurable impact on rainfall trends in Victoria, Australia.

 

Reference

Rahmat, S.N., Jayasuriya, N. and Bhuiyan, M.A. 2015. Precipitation trends in Victoria, Australia. Journal of Water and Climate Change 6: 278-287.

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