Arctic thaw quickening threatens trillion-dollar costs - report

[janclaes47]

On 25/04/2017 at 10:59 AM, impulse said:

Melt enough glaciers to stop the Gulf Stream conveyor, and Europe could go into another ice age...

 

Did you say ANOTHER ice age?

 

So that mean there was already one previously.

 

Was that one also caused by human activities and burning fossil fuels?

[ilostmypassword]

1 hour ago, rickudon said:

Interesting ....... Supposedly rice grows best at around 30 degrees centigrade (depends on variety), but can survive considerably higher temperatures, up to over 50 centigrade. Although higher temperatures might decrease harvests in some countries, the biggest temperature factor affecting rice is cold ..... outside of the tropics it is a big limiting factor. Any fall in tropical production would probably be matched by increased temperate zone harvests. Wheat, on the other hand, is much more vulnerable to a rise in temperature (especially because a lot is grown without irrigation) - although i suppose it would allow bigger harvests in Canada and Siberia .....

 

This document gives some idea of rice temperature tolerance (easy to find info on cold tolerance, high temperature tolerance less so). Bare in mind that changing to a more heat tolerant strain could offset yield losses.

 

https://agritrop.cirad.fr/570279/1/document_570279.pdf

And what grain would replace rice in the tropics? And what grains would rice replace in temperate zones?

[ilostmypassword]

1 hour ago, janclaes47 said:

 

Did you say ANOTHER ice age?

 

So that mean there was already one previously.

 

Was that one also caused by human activities and burning fossil fuels?

Except of course that the previous ice age was a global phenomenon whereas the ice age referred to here would not be.  But even if it was the same phenomenon, ice ages ordinarily take thousands of years to develo? You think it's a good idea to speed up the next one's advent by thousands of years.

(And to be technical about it. the planet currently is in an ice age. Right now it's an interglacial period)

[nauseus]

19 hours ago, Grouse said:

This is first class!

 

Some might find the statistics a little heavy going but I was enthralled! Such erudition!

 

Recommended for educated people everywhere 

 

Trumpsters and Brexiters will find Coke and Popcorn elsewhere ?

Yes it was a good lecture, easy to understand and and factually, in-line with my university studies and resultant understanding of the earth sciences. A pity though, that you had to add the (off-topic) condescending comments involving education and politics.   

[RPCVguy]

5 hours ago, rickudon said:

Interesting ....... Supposedly rice grows best at around 30 degrees centigrade (depends on variety), but can survive considerably higher temperatures, up to over 50 centigrade. Although higher temperatures might decrease harvests in some countries, the biggest temperature factor affecting rice is cold ..... outside of the tropics it is a big limiting factor. Any fall in tropical production would probably be matched by increased temperate zone harvests. Wheat, on the other hand, is much more vulnerable to a rise in temperature (especially because a lot is grown without irrigation) - although i suppose it would allow bigger harvests in Canada and Siberia .....

 

This document gives some idea of rice temperature tolerance (easy to find info on cold tolerance, high temperature tolerance less so). Bare in mind that changing to a more heat tolerant strain could offset yield losses.

 

https://agritrop.cirad.fr/570279/1/document_570279.pdf

 

That is a fair report as to rice and its cardinal growing temperatures. I downloaded and read the PDF  and wish to highlight two early statements:

"Climatic changes are one of the major problems in rice cultivation. Using a number of scenarios, the Intergovernmental Panel on Climate Change (IPCC) estimates that between 1990 and 2100, temperature is likely to rise by 1.4 to 5.8°C. Although the likely effect of this rise in temperature is regionally dependant, it is thought that in most tropical and subtropical areas (where tropical rice is grown), crop yields are likely to decrease with increasing temperature, exacerbated by a reduction in rainfall ( Parent et al., 2010)."

and

"Rice is consumed as a grain almost exclusively by humans, supplying 20% of daily calories for the world population."

 

Where that study also left off, but PNAS and others have researched is that for grains,  measuring rate of leaf growth is not as useful as measuring the yield per stalk of rice grains.

It has the same general shape and analysis as the one I used by Prof David Battisti whose background and audience was mostly applicable to corn, which has an overall lower set of preferred temperatures than rice - especially Jasmine Rice upon which Thailand is dependent.


|I specifically gave the video link to the lecture so as to assist people in understanding the significance of that curve as relates to climate change and expected temperature ranges year-to-year and over the growing seasons as this century progresses.

To convey the impact as to what is expected to be "normal" as well as any year being above or below normal in the region of a crop, Prof. Battisti used histograms (just like in the PDF you provided) to compare early and late century middle of the road expectations as to daily temperatures in France and in sub-Sahara Africa. In both cases the normal year was hotter than the hottest year experienced through 2006. Do watch the video to understand how those conclusions are reached.
https://www.youtube.com/watch?v=YToMoNPwTFc&t=2090

 

Back to the key factor for rice.  High nighttime temperatures or daily minimum temperatures would reduce the germination percentage of pollen grain and repress spikelet fertility. This is communicated in a BBC article reporting: "Although yields have risen as farming methods improved, the rate of growth has slowed as nights have grown warmer. By contrast, higher temperatures during the day were related to higher yields; but the effect was less than the yield-reducing impact of warmer nights."
http://www.bbc.com/news/science-environment-10918591

and that article was from this PNAS report:
http://www.pnas.org/content/101/27/9971.full

and more recently in various rice studies such as this from 2016:
https://www.tandfonline.com/doi/full/10.1080/1343943X.2015.1128091

Each of these reports predicts a reduction of rice yields in the range of 10% or more per degree Celsius increase over the optimal temperature. That is surely an issue of Food Security for Thailand. Taken globally, those histograms plotted as a world map point to the conclusion  Ilostmypassword asked so well and concisely: "And what grain would replace rice in the tropics? And what grains would rice replace in temperate zones?"

 

 

 

 

Edited March 11, 2018 by RPCVguy

[RPCVguy]

Those above posts detail the risks, here's what can be done:

 

To improve rice crop yields, we need to have clearer night skies so daytime heat can radiate to space with less intervention. Late afternoon and evening monsoonal rains do this, but industrial aerosol pollution causes problems. It interferes with / inhibits rains by changing the size of moisture condensing in the air, and add to the blanketing effect at night.
https://www.ncbi.nlm.nih.gov/pmc/articles/PMC1450178/
 

Reforestation can help mitigate this. Forests absorb the pollution, release microbes into the air that enhance rainfall, perpetuating the transpiration effect trees need to flourish inland. Humans need to actively reforest the lands, especially the upper hillsides where water absorption avoids erosion and creates long term moisture in the hills to last through the dry seasons. Adding swales on level contour lines accelerates the capture of rain water. Using nitrogen fixing plants in abundance (tamarind, mimosa, thorny acacia (pak chaom), ผักกะฐิน (pakateen), the various peas & beans, etc.)  so as to be able to chop and drop to build the carbonized soil sponges being described and naturally adds fertility and pest interference for fruit and hardwood trees planted through the same mixed growth area.

 

Walter Jehne offers good advice worth doing as much of as we can get adopted.
See

Adopting his ideas have benefits on regional climate, and sequesters carbon rapidly, though there are balance points as forests mature. The hydrological cycles of hills, forests and the planet are important. While I like Jehne's approach, I disagree with him on what is causing the temperature imbalances. I see the 45% increase in GHG as the imbalance that is tipping the scales towards warming. Rainfall limits the increases in airborne moisture allowing it to increase only within the range of relative humidity at the slightly higher temperatures.

 

[rickudon]

I'm not questioning that Global warming is an issue for cereal production. But for rice, i suspect water is a more critical issue in the tropics. We do not know if global warming will increase, decrease or have little affect on water availability in the tropics, but most people are inclined to think less water. Rice is a water hungry crop. But also, in Thailand rice productivity is quite low, especially in Isaan. Most farms are small, poorly mechanised and with a low level of inputs, much depends on natural rainfall rather than irrigation. And a lot of the rice fields are derelict as currently economic returns are negligible. But Thailand still produces far more rice than it needs. I wouldn't say rice is a food security issue for Thailand, more an economic/export related one.

 

As for what you replace rice with in the tropics, that is a complex mix of variety, temperature, water and economics. Certainly if water is an issue you could move over to maize or sorghum.

 

As for what crops rice would replace in temperate areas, mainly would depend on if it was more economic to grow rice or not. I suspect that mainly it would just be greater productivity per hectare. I think Wheat has a far bigger problem with global warming than rice, because it is grown in many areas where high temperatures and water are already the main limiting factors.