Overall Results - Climate Change: Identification and Projections - page 98

over the last century. Whatever the case in point, the relative accuracy with
which sensitivity S irr is estimated leaves no space for any doubt.

The second conclusion is less clear-cut. It comes down to stating that the
observations do not allow us to determine climate sensitivity with any great
confidence, not even the sign. Indeed, some free models display estimates of
negative climate sensitivity, even significantly so (up to 2.46 ° C). For such

values to be reached, the positive effect of anthropogenic GHGs would have
to be much lower than the IPCC assumptions, which cannot be ruled out, but
also, the negative effects of aerosols and changes in land use would have to
reach extreme level, which is more doubtful.

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