16rsta.royalsocietypublishing.orgP h i l .T r a n s .R .S o c .A376:20160452 ........................................................
Figure10. Distributionsofchangesinrun-offformeanflowssimulatedbytheJULESecosystem–hydrologymodelunderthe
ensembleofsixclimateprojectionsat1.5 °C(blue)and2 °C(orange)globalwarming.Boxesshowthe25thand75thpercentile
changes, whiskers show the range, circles show the four projections that do not define the ends of the range, and crosses
showtheensemblemeans.Numbersinsquarebracketsshowtheensemble-meanflowinthebaseline,inmillimetresofrain
equivalent.
all members ( ﬁgure 12 ). This is not the case for the precipitation and run-off results; for those
quantities, there is substantial overlap in the ranges of changes at 2°C and 1.5°C, so there is not a
consistent picture of how much wetter or drier the world is projected to be in this ensemble, even
though it involves a single atmosphere model.
For TXx, the difference between 2°C and 1.5°C global warming is larger than the 0.5°C
difference in global mean temperature across most of the land surface in all ensemble members
(ﬁgure 14). Although some ensemble members simulate local temperatures to be higher at 1.5°C
global warming than 2°C in some small regions, these are relatively localized and most regions
are cooler at 1.5°C global warming than 2°C. In many regions, the difference is between 0.5°C and
1.0°C, but many other regions see larger differences. In several ensemble members, the difference
is 1.5°C, 2°C or larger in large parts of North America, South America, Europe and China.
For example, over parts of Europe, where annual maximum daily temperature was projected
to increase by over 5°C for a 2°C global warming, the local increase is limited to 3–4°C for
1.5°C global warming. Limiting global warming by half a degree Celsius would, therefore, limit
maximum temperatures by three or four times as much in those areas (ﬁgure 14).
At 1.5°C global warming, although the increases in TXx are smaller than at 2°C, these increases
show similar geographical patterns as for 2°C in all ensemble members, with larger changes in
continental interiors especially in the mid-latitudes (not shown).
The percentage of days exceeding the 90th percentile of daily temperature (Tx90p) also
increases less at 1.5°C global warming than at 2°C ( ﬁgure 15 ). The largest reductions are in the
tropics, where the largest increase was seen at 2°C; whereas at 2°C global warming, 50% or more