Current warming and likely future impacts - Climate Change: Biological and Human Aspects - page 264

average 6.1 km ( 2.4 km with 95% confidence) northwards, or the same number of

metres upwards, per decade. Phenologically a total of 172 species of herb, butterfly,
shrub, tree and amphibian revealed an earlier spring timing of 2.3 days per decade
with a 95% confidence range between 1.7 and 3.2 days' advancement per decade.
With regards to phenology (see section 6.1.4), purely on the basis of either advance-
ment or delay of spring events (i.e. no quantification, just direction of change), such
as frog breeding, bird nesting, first flowering, tree burst and arrival of migrant birds
and butterflies, of 677 species assessed from the literature 27% showed no change,
9% showed delayed spring events (the opposite of what you would expect with global
warming) and 62% showed spring advancement. In summary, about 87% of species
that showed any change showed the change one might expect with climatic warming.
Interestingly, published in the same issue of Nature as this study was another that
also looked at the fingerprint of global warming on wild plants and animals (Root
et al., 2003). Again there was an association with the IPCC, in that four out of the six
researchers were previously members of the IPCC's 2001 Working Group II and the
study by Root and colleagues built on some of the literature examined by that group.
There is little doubt that their motivation to express a separate analysis arose out of
the Working Group II's own internal debate, of which Parmesan and Yohe were aware
(see above), that there was a 'divergence of opinion'. It is important to note that Root
et al. only included those studies that (1) spanned 10 years or more, (2) showed that
at least one species changed over time and (3) found either a phenological change
associated with temperature or vice versa. However, in addition they attempted to
see whether there were any correlations between climatic cycles (see section 5.1.5),
such as the North Atlantic Oscillation (NAO) and the El Ni no Southern Oscillation
(ENSO), and phenological change. Of more than 2600 species covered in the 143
studies that met the researchers' criteria they found that more than 80% of species of
animal (molluscs to mammals) and plant (grasses to trees) exhibited change in the
direction that one might expect with global warming. They concluded that the balance
of evidence is that there is a discernable fingerprint of recent decadal warming on
animal and plant populations. Whereas the authors admit that their study selection
is open to possible bias, it is interesting to note that this figure of more than 80%
appears to broadly corroborate Parmesan and Yohe's figure of 87%.
Camille Parmesan and Gary Yohe's seminal work was done in 2003 but, as ever
with research, science moves on. In 2011 a British-based team headed by I-Ching
Chen and Jane Hill reported an even faster terrestrial species shift in response to
warming. As with the Parmesan-Yohe study, Chen et al. used a meta-analysis. Their
results indicate that distributions of species have recently shifted to higher elevations
at a median rate of 11.0 m per decade, and to higher latitudes at a median rate of
16.9 km per decade. These rates are approximately two and three times faster than
previously reported (6.1 km latitudinally, or metres vertically, and per decade). The
distances moved by species were greatest in studies from the meta-analysis showing
the highest levels of warming, with average latitudinal shifts being generally (but
not always) sufficient to track, or serve as a proxies for, temperature changes. The
authors also note that not all species responded by shifting proportionally to the
amount of warming. As noted before (for example, section 4.6.4), some species can
migrate faster than others. Furthermore, climate change is multifactoral and not just

±