Tag: co2

Projecting the Impacts of Rising CO2 on Future Crop Yields in Germany

Noting that the influence of atmospheric CO2 on crop growth is “still a matter of debate,” and that “to date, no comprehensive approach exists that would represent all related aspects and interactions [of elevated CO2 and climate change on crop yields] within a single modeling environment,” Degener (2015) set out to accomplish just that by estimating the influence of elevated CO2 on the biomass yields of ten different crops in the area of Niedersachsen, Germany over the course of the 21st century.

To accomplish this lofty objective the German researcher combined soil and projected future climate data (temperature and precipitation) into the BIOSTAR crop model and examined the annual difference in yield outputs for each of the ten crops (winter wheat, barley, rye, triticale, three maize varieties, sunflower, sorghum and spring wheat) under a constant CO2 regime of 390 ppm and a second scenario in which atmospheric CO2 increased annually through the year 2100 according to the IPCC’s SRES A1B scenario. Degener then calculated the difference between the two model runs so as to estimate the quantitative influence of elevated CO2 on projected future crop yields. And what did that difference reveal?

As shown in the figure below, Degener reports that “rising [CO2] concentrations will play a central role in keeping future yields of all crops above or around today’s level.” Such a central, overall finding is significant considering Degener notes that future temperatures and precipitation within the model both changed in a way that was “detrimental to the growth of crops” (higher temperatures and less precipitation). Yet despite an increasingly hostile growing environment, according to the German researcher, not only was the “negative climatic effect balanced out, it [was] reversed by a rise in CO2” (emphasis added), leading to yield increases on the order of 25 to 60 percent.

Figure 1. Biomass yield difference (percent change) between model runs of constant and changing atmospheric CO2 concentration. A value of +20% indicates biomass yields are 20% higher when modeled using increasing CO2 values with time (according to the SRES A1B scenario of the IPCC) instead of a fixed 390 ppm for the entire run.

Figure 1. Biomass yield difference (percent change) between model runs of constant and changing atmospheric CO2 concentration. A value of +20% indicates biomass yields are 20% higher when modeled using increasing CO2 values with time (according to the SRES A1B scenario of the IPCC) instead of a fixed 390 ppm for the entire run.

The results of this model-based study fall in line with the previous work of Idso (2013), who calculated similar CO2-induced benefits on global crop production by mid-century based on real-world experimental data, both of which studies reveal that policy prescriptions designed to limit the upward trajectory of atmospheric CO2 concentrations can have very real, and potentially serious, repercussions for global food security.



Degener, J.F. 2015. Atmospheric CO2 fertilization effects on biomass yields of 10 crops in northern Germany. Frontiers in Environmental Science 3: 48, doi: 10.3389/fenvs.2015.00048.

Idso, C.D. 2013. The Positive Externalities of Carbon Dioxide: Estimating the Monetary Benefits of Rising Atmospheric CO2 Concentrations on Global Food Production. Center for the Study of Carbon Dioxide and Global Change, Tempe, AZ.

A Diatom’s Response to Three Levels of CO2

Phaeodactylum tricornutum is a marine diatom that is also a potential alternative energy source due to its high growth rates and lipid (fat) content, the latter of which – according to Wikipedia  – constitutes about 20 to 30 percent of total dry cell weight under standard culture conditions. Given as much, this species is of interest to scientists, such as the seven-member research team of Wu et al. (2015), who recently conducted an experiment to determine how this potential biofuel responds to different levels of atmospheric CO2. More specifically, the group of Chinese researchers studied the response of P. tricornutum to three levels of CO2 (150, 350 and 1500 parts per million (ppm)) over a period of seven days. 

For comparative purposes, a CO2 concentration of 150ppm is around the threshold value required to sustain plant growth on this earth. We came perilously close to this at the nadir of the last ice age. 350ppm is the concentration from a quarter-century ago (we’re around 400ppm now) and 1500ppm is quite a bit higher than even the most optimistic forecasts can get it to around 2100.

And what did they learn? As shown in the figure below, diatom growth rates rose with the level of CO2 treatment. The growth at 350 and 1500 ppm treatments were approximately 70 and 192 percent greater than that observed in the lowest CO2 treatment (150 ppm). And those values may be conservative, given that growth rates at the two higher CO2 concentrations appear to still be rising at the end of the experiment on day 7 (i.e., the green and red lines have not peaked). Similar trends were seen in culture dry weights, where the mean dry weight values reported for the medium and high CO2 treatments were 31 percent and 195 percent greater than in the low CO2 treatment. Lastly, lipid content, expressed as a percent of dry cell weight, amounted to 33, 36 and 54 percent in the 150, 350 and 1500 ppm treatments, respectively.

In discussing their findings, Wu et al. note their results are “consistent with numerous previous studies that higher levels of CO2 support higher growth rates.” And, they further demonstrate the possible viability of using P. tricornutum as a biofuel, which many persons today consider an added benefit.



Wu, S., Huang, A., Zhang, B., Huan, L., Zhao, P., Lin, A. and Wang, G. 2015. Enzyme activity highlights the importance of the oxidative pentose phosphate pathway in lipid accumulation and growth of Phaeodactylum tricornutum under CO2 concentration. Biotechnology for Biofuels 8: 78, DOI 10.1186/s13068-015-0262-7.

Two Millennia of Snowfall Accumulation in Antarctica

Providing the rationale for their work, Roberts et al. (2015) write that “the short and sparse instrumental record in the high latitudes of the Southern Hemisphere means investigating long-term precipitation variability in this region is difficult without access to appropriate proxy records.” It was therefore the objective of this team of nine researchers to extend the duration of the Law Dome, East Antarctica, snowfall accumulation record back in time an additional 750 years so that it would cover over two millennia.

The resultant 2035 year-long proxy (22 BC to 2012 AD) is presented in the figure below. As reported by the authors, the average long-term snow accumulation rate was calculated as 0.686 m yr-1 (27 inches) ice equivalent, which rate they say “is in agreement with previous estimates, and further supports the notion that there is no long-term trend in snow accumulation rates, or that any trend is constant and linear over the [2035-year] period of measurement.”

If this number seems low for such an icy continent, the fact is that most high-latitude locations in both hemispheres would qualify as deserts based upon annual precipitation. In many places, it is literally “too cold to snow” as the frigid air can hold only tiny amounts of moisture.

There were several decadal-scale oscillations in the record, described by the authors as “common,” with “74 events (33 positive and 41 negative) of at least a 10-year duration in the record.”  The three longest periods of above average integrated snowfall occurred over the intervals 380-442, 727-783, and 1970-2009, while the three longest periods of below average integrated snowfall occurred during 663-704, 933-975, and 1429-1468.

Want Better Tomatoes? Add Carbon Dioxide and a Pinch of Salt!

Who isn’t nuts about fresh tomatoes plucked from a garden at the peak of ripeness? And who doesn’t bask in the adulation of those to whom we give them?

According to work recently published by Maria Sanchez-González et al. (2015), the more years you garden, the more tasty your tomatoes are likely to get, as atmospheric carbon dioxide increases. And, if you add a pinch of salt to the soil, they’ll taste even better.

Here’s the story:

The authors note “the South-Eastern region of Spain is an important area for both production and exportation of very high quality tomatoes for fresh consumption.” This is primarily due to favorable growing conditions such as a mild climate, good soils and saline waters that promote “exceptional fruit quality of some varieties,” including the Raf tomato hybrid. However, Sánchez-González et al. additionally note that, “despite the high value of Raf tomatoes in the Spanish national market, their productivity is relatively low and the consumer does not always get an acceptable quality, often because the fruit growth conditions, mainly thermal and osmotic, were not adequate.” Against this backdrop, the team of six researchers set out to determine if they could improve the production value of this high value commercial crop by manipulating the environmental conditions in which the tomatoes are grown. To accomplish this objective, they grew hybrid Raf tomato plants (Lycopersicon esculentum Mill. cv. Delizia) in controlled environment greenhouses at two salinity levels (low and high) under ambient (350 ppm) and elevated (800 ppm) CO2 concentrations. Then over the course of the growing season, and at harvest, they measured several parameters related to the growth and quality of the hybrid tomatoes. And what did their analysis of those measurements reveal?

New Paper: Why Sustainability Standards for Biofuel Production Make Little Economic Sense

The U.S. sustainability standard currently requires ethanol production to emit at least 20% less CO2 than the gasoline it is assumed to replace. In a new study, authors Harry de Gorter and David R. Just argue that sustainability standards for ethanol are, by definition, illogical and ineffective. Moreover, say de Gorter and Just, those standards divert attention from the contradictions and inefficiencies of ethanol import tariffs, tax credits, mandates, and subsidies, all of which exist whether ethanol is sustainable or not.