14rsta.royalsocietypublishing.orgP h i l .T r a n s .R .S o c .A376:20160452 ........................................................
ACCESS1-0
–1.00 –0.75 –0.50 –0.25 0 0.25 0.50 0.75 1.00
IPSL-CM5A-LR
ensemble mean
change in vulnerability to food insecurity
IPSL-CM5A-MR MIROC-ESM-CHEM
GFDL-ESM2M
Figure8. ChangeinHungerandClimateVulnerabilityIndexrelativetobaselinecalculatedforsimulatedclimatestatesat2 °C
globalwarming,forfiveindividualHadGEM3simulationsdrivenbySSTsandSICsfromdifferentmembersoftheCMIP5ensemble,
andtheensemblemean.
Four countries show ensemble-mean HCVI values at 2°C global warming that are higher
than any seen in the baseline climate; these are Oman, Bangladesh, Mauritania and Yemen.
The implication of such HCVI values is that climate change at 2°C is projected to cause levels
of vulnerability to food insecurity that are greater than any seen in the present day. For
individual ensemble members, the number of countries with ‘unprecedented’ HCVI values at
2°C varies from three to seven. Conversely, many countries in the baseline climate have levels
of vulnerability to food insecurity that are greater than those expected in other countries under
2°C global warming. This suggests that other factors are already posing greater risk for food
insecurity than 2°C climate change is expected to cause in other countries, so the increased risk
from climate change should not overshadow the need to reduce vulnerability to food insecurity
arising from non-climatic factors. There is scope to reduce vulnerability to food insecurity by
addressing various socio-economic issues in such counties.
The JULES simulations show a general tendency towards increased run-off over
approximately half of the land surface ( ﬁgure 9 ) and the majority of the major river basins
assessed (ﬁgure 10), but with large regional uncertainties including the possibility of decreased
ﬂows in many basins. The ensemble-mean change in mean streamﬂow shows an increase of
between 5 and 25% over most of the Northern Hemisphere land surface, with some regions seeing
an increase of over 50% at 2°C global warming. Notable exceptions to this are western Europe and
southcentral USA, which see less than a 5% change in run-off, and the already very dry region of
the Sahara Desert where the existing very small run-off become even smaller.
Ensemble-mean projected changes in low run-off ﬂows are generally larger ( ﬁgure 11 ), with
the regions seeing an increase in mean run-off seeing a larger percentage increase in low
run-off—over 75% increases over much of North America, Eastern Europe and Asia. Note that
this does not necessarily imply a larger increase in absolute low ﬂow compared to absolute mean
ﬂow, because the baseline is (by deﬁnition) smaller for low ﬂows. In western Europe, where the
changes in mean ﬂows were less than 5%, the ensemble-mean low ﬂow decreases by between 5