New Research Shows How Different Greenhouse Gases Adversely Affect Crops

One of the tropes circulated by climate deniers has been that "Excess carbon dioxide is good for plants and especially crops". In other words, CO2 even at exceptionally high levels, is not really a pollutant, but something to help us attain better crop yields. While climate scientists and environmentalists have tried to correct this, i.e showing that excess CO2 actually propels "super weeds" which kill crops and that necessitates ever stronger weedicides like agents as: 2, 4- D, dicamba and paraquat, the effects have been nominal. (See also:The Wall Street Journal  June 4, 2010, p A16, 'Superweeds Trigger New Arms Race')

The deniers, for their argument, probably invoked the (summary) chemical equation most of us learned in high school biology for photosynthesis:

6 CO2 +   6 H20 + light energy  ->  C6 H12 O6  + 6 O2

Thus, the carbon dioxide (6 molecules) combined with six of oxygen and adding in radiant energy (sunlight) gives glucose plus oxygen. What could be wrong? Well, a lot it there is too much carbon dioxide.

But this example, illustrates the recurring problem of exactly how any greenhouse gas affects crop yields. Now thanks to new work by Drew T. Shindell, e.g.

http://onlinelibrary.wiley.com/doi/10.1002/2016EF000377/full

We are finally getting some useful answers. While it's been known that carbon dioxide is the largest driver of climate change, Shindell found that other anthropogenic emissions cause more damage to actual crop yields.  Among the culprits named in the past: methane, halocarbons (used in refrigeration and air conditioning),  and black carbon (from biomass and fossil fuel burning)

In his paper published in Earth's Future, Shindell sought to create a more complete picture of human-caused emissions.  He did this by assembling data from his previous studies as well as the IPCC's fourth and fifth assessment reports and crop yield data from previous work.  Shindell then created a model to determine the effect that individual greenhouse gases have on global temperatures, precipitation, carbon dioxide and ozone - all of which affect crop success.

Shindell's model revealed that in the short term (i.e. 1st decade after release of emissions), the greatest damage to crops per ton comes from black carbon and halocarbons. Methane emissions come next, given that the gas (CH4) increases surface ozone which causes harmful chlorosis, i.e. a yellowing of leaves.

Shindell found the effects of CO2 are more complicated, For example, as the amount in the atmosphere increases, crop yields initially do as well. But as the CO2 emissions continue to contribute to climate warming the overall impact becomes negative with any benefits originally accruing basically being outweighed by deleterious effects after only 10 years.

Overall, Shindell's model indicates that up to 93 percent of crop losses through the rest of the century will be caused from non-carbon dioxide emissions with methane the most damaging. (Let us also bear in mind the most massive methane outgassing, as from melting permafrost in the Arctic, is triggered by much higher warming from carbon dioxide)

The most intriguing aspect of Shindell's paper is in where it shows how mitigation procedures can increase crop yields. For reduced CO2 alone, for example, crop yields would go up 3 percent. If methane is suitably reduced (which also means CO2 and warming is reduced) we can expect a 16 percent increase in crop yields.

On the other hand, under a high emissions scenario for all greenhouse gases (likely under Trump) there will be nearly 25 percent crop losses by the end of the century. Given the world's population is expected to balloon to 11 billion or more, we are looking at extreme hunger, starvation. This will be in the most densely populated regions such as Africa.

Without a doubt, Shindell's work provides a solid basis for decisions by policy makers. The question now is whether they will even read his work, and then act on it.

The Weeds Are Winning -And Allergies Increasing - Thanks to Global Warming

Pigweed - now growing as if on 'afterburners' with CO2 the fuel.

 

The recent (June 2, Personal Journal, p. 2) article in The Wall Street Journal ('Allergies Worse in Some Years?')  provided a sobering reminder of how conditions on Earth have radically changed in just five years, enabling a much longer and miserable allergy season as well as the continued growth of super weeds and hyper-pollination. All this owing to global warming's advance which too many still deny.

The article quoted a fellow with the American Academy of Allergy, Asthma and Immunology, in noting how "the allergy season is so weather driven, short term and long term". He also wasn't inhibited about implicating global warming-climate change, observing:

"In northern states where global warming is already having an effect, winter is shorter and spring might come earlier, which can lengthen the pollen season".

He went on to indicate that a "dream year" for allergy sufferers would be one in which there is a long winter and rain in the spring" given the rain "washes out tree pollen" and a longer winter delays the pollen season.

Alas, that trend is not in the cards, given global warming's pattern is for ever shorter winters ultimately ending in the first "year of no seasons"  by 2040 and possibly as early as 2030. In such a nightmarish world, allergy sufferers would be bombarded year round and even rains would be of little help - amping up grasses and weeds that people now mainly endure in late summer - such as ragweed.


Five years ago one beheld in the The Wall Street Journal (June 4, p A16, 'Superweeds Trigger New Arms Race'; June 21, p. D1, 'Least Welcome Sign of Summer') the announcement of the arrival of "super weeds".

According to that account, "by the middle of this decade"  (2015)  "at least 40% of U.S. corn and soybean crops will harbor Roundup resistant super weeds". Roundup, and especially Monsanto's Roundup -ready seeds, have been amongst the biggest "success stories" in the domain of weed control, primarily because of its primary constituent - glyphosate- which is one of the least toxic around. As one farmer cited in the first article put it: If glyphosate isn't the safest herbicide, it's damned close".

At the time of the writing Roundup and generic competitors were used on nearly 4 times as many acres as any other herbicide, but true to evolutionary dictates and principles - the weeds had adapted, and new, hardier variants emerged resistant to the weedicides. Many scientists agree that enhanced CO2 plays no small role in facilitating this adaptation, since stronger, larger weeds are the result.

One variant of pigweed reported on a farmer's property grew to six feet in height on a stalk the width of a baseball bat's wide end. The weed was so tough, it damaged mechanical parts of his cotton picking equipment and had to be rooted out by hand. The farmer had to hire 20 labor hands to attack the weeds using hoes, even then breaking a number of them.

The emergence of these super weeds, especially as threats to farm productivity had already convinced many farmers they had to resort to much more toxic weedicides to get the job done. That included using such infamous carcinogenic agents as: 2, 4- D, dicamba and paraquat. But critics warned given the uncontrolled factors afoot, such as ever increasing CO2 concentrations (now tipping at nearly 400 ppm) this solution may be 'too little, too late'.

Today, and as I've  noted in previous blog posts, the situation has gotten so bad that a new GMO version of ENLIST -enhanced crops has entered the food supply. Enlist DUO engenders a new potent herbicide mix of 2,4 D and glyphosate which Mehmet Oz (in his Sept. 19, 2014 show) described as a "health calamity" because of the likely effects including, non-Hodgkins lymphoma, Parkinson's disease and even Alzheimer's disease, see also:

http://brane-space.blogspot.com/2014/03/alzheimers-epidemic-fro-eating-gmo.html

As noted therein:

"GMO foods contain glyphosate, a horrifically destructive chemical that saps nutrients from foods and quite literally makes them toxic to consume."


We clearly have even bigger concerns going forward than enhanced allergy intensity - as bad as that will be. Indeed, if we are headed for an even larger increment in warming (4C or 6C by 2100) the situation could well become intolerable for billons. In addition given this new increment we could see the first year of no seasons much earlier, even before 2030. While climate change deniers are yukking it up, the weeds are on overdrive thanks to a greenhouse gas the deniers dismiss as a threat. Go figure!

See also:

http://brane-space.blogspot.jp/2015/05/the-new-reality-global-mean-temperature.html