Climate Change and Food Security
Science: IPCC Assessment 2007
Our commitments to climate change and food production losses
Global crop yield is at risk of decline at a temperature increase of 1.0°C
(IPCC WG 2 Technical report 07).
IN ALL REGIONS
WITH INCREASING WARMING
AND CLIMATE CHANGE
Coasts: models indicate that salination from sea level rise and coastal damage spreads far inland as well as up river estuaries and deltas that are food growing regions.
Health: food production in the developing nations depends on human labour, and human populations in these regions will be badly affected by multiple adverse health impacts from climate change.
Ecosystems and species: even agricultural productivity in developed nations depends on the health of the regional ecosystems and biodiversity, one example being pollinators.
Water: both extremes of precipitation and drought that will be increased by global climate change disaster on food productivity.
Small glaciers: huge populations depend on seasonal spring run-off from small mountain top places for crop irrigation. Melting the lease will initially cause flooding of the agricultural regions they feed into followed over time by progressively less naturally irrigating water for crop production.
IPCC model results composite by NRC
The IPCC presentation has circled in black the world's best food producing regions that will be hit by increased dryness and droughts. .
Change in wet and dry days mid A1B scenario 2000 to 2080. IPCC 2007
NB. Too much and too little rain are damaging to crops
0.5C safety limit.
A temperature increase above 1.0ºC* is /or was (too) dangerous for water food and health security to the most climate change populations- especially in the developing nations dependent on subsistence/small holder food production, coastal populations,and populations dependent on glacial spring run -off (over a billion).
*Cochabamba Peoples climate agreement , The Case for Young People and Nature
Long term food security
Temperature does not stop increasing at 2100. It will almost double after 2100.
With respect to food security to avoid, for example, a disastrous 2ºC temperature increase affecting all future generations we have to limit the 2100 increase to 1.2ºC (at a stabilized atmospheric GHG concentration).
To avoid a long term increase of 3ºC that will destroy most if not all of the planet's agricultural food production capacity we have to limit the increase by 2100 to 1.6ºC.
The IPCC assessment on food relies on climate crop models. In addition to the food production losses by the few agricultural changes that are captured by the models, other adverse impacts (added to the above chart) will greatly added to further crop losses such as drought, drying, torrential rains and floods (ie extreme weather events).
N.B. the IPCC assessment of food impacts is not a risk assessment, as pointed out by the National Research Council greenhouse gas report in 2010 because large impacts are not captured by the climate crop models.
IPCC Summary for Policy Makers.
Crop productivity is projected to increase slightly at mid - to high latitudes for local mean temperature increases of up to 1-3°C (1 - 2.6C global from pre-1900) depending on the crop, and then decrease beyond that.
At lower latitudes, especially seasonally dry and tropical regions, crop productivity is projected to decrease for even small local temperature increases 1.0 -2°C (0.8- 1.5C Global from pre-1900)
Globally, the potential for food production is projected to increase with increases in local average temperature over a range of 1.0-3°C (1- 2.6C global from pre-1900), but above this it is projected to decrease.
Increases in the frequency of droughts and floods are projected to affect local crop production negatively, especially in subsistence sectors at low latitudes. (IPCC 2007)
Globally, some 3.6 billion ha (about 27% of the Earth's land surface) are too dry for rain fed agriculture.
Considering water availability, only about 1.8% of these dry zones are suitable for producing cereal crops under irrigation.
This is the worst case IPCC scenario that global emissions are tracking
The climate crop models on which the IPCC relies to assess global climate change impacts on food production fail to capture about half the many inevitable impacts.
The scientists think that the CO2 fertilization positive effect from experiments in artificial environments are over estimates of the real world benefits for agriculture.
Even so, the IPCC climate crop models are based on CO2 research lab benefits.
Global climate change will take progressively more land out of food production as temperatures increase. There is an established trend of increasing global droughts since 1860 and there is total agreement that under increased global warming droughts will increase.
22.214.171.124 Review of crop impacts versus incremental temperature change.
The results of such (computer model) simulations are generally highly uncertain due to many factors, including large discrepancies in GCM (different models) predictions of regional precipitation change, poor representation of impacts of extreme events and the assumed strength of CO2 fertilisation.
Nevertheless, these summaries indicate that in mid- to high-latitude regions, moderate to medium local increases in temperature 1ºC to 3ºC (1C - 2.6C global from pre-1900), across a range of CO2 concentrations and rainfall changes, can have small beneficial impacts on the main cereal crops. Further warming has increasingly negative impacts.
In low-latitude regions, these simulations indicate that even moderate temperature increases 1ºC to 2ºCFor temperature increases more than 3°C
(0.8-1.5C global pre-1900) are likely to have negative yield impacts for major cereal crops.
(2.6C global from pre-1900), average impacts are stressful to all crops assessed and to all regions.
The low and mid-to-high latitude regions encompass the majority of global cereal production area. This suggests that global production potential, ..., is threatened at +1°C (1C global from pre-1900) local temperature change and can accommodate no more that +3°C (2.6C global from pre-1900) before beginning to decline.
However the assumed temperate region yield increase may not happen because the above linear IPPC model results to not capture extreme events.
Modelling studies suggest that increasing frequency of crop loss
due to extreme events, such as droughts and heavy precipitation,
may overcome positive effects of moderate temperature increase
The IPCC results are very important to understand because it is only the IPCC assessment that is recognized by policy makers and governments.
Note. Local temperature changes are converted to global temperature levels using a value of 1.5°C local per global °C for mid-to-high latitudes and 1.2°C local per global °C for low latitudes (NRC). From 2000 temperature increases are converted to from pre-industrial by adding 0.5° C (IPCC)