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Chris,
The problem with your suggestion is that measurements of temperature
(unlike precipitation) are necessarily related to an arbitrary zero.
Thus, a "1%" change in the numerical value is meaningless.
For example, if the Atlantic Water entering the Barents Sea was to
warm from 3 to 4 Celsius, it might look like a 33% increase but it
could just as well be a 5% increase (in Fahrenheit) or even 0.4% (in
Kelvin). Even if we just used a "modified Celsius" for oceanographic
purposes, with zero at the freezing point of seawater, rather than
fresh, the change would be a "mere" 19%. With such a spread of
numerical values, none of them can convey any understanding.
You could try defining a "biological zero", at which all biological
activity would shut down, but that is likely to vary from one
ecosystem to another, which would further complicate interpreting
percentage changes.
Better to stick to a straightforward, understandable measure (e.g.
increases in Celsius units) for the simple stuff and then get busy
with understanding and explaining projections in ecological and
ecosystem terms. For the Arctic Ocean, that won't be a matter of
temperature increases so much as the degree of penetration of various
water masses and the ecosystems found within them, the dominant effect
of salinity on seawater density once temperatures are around the
freezing point, the implications of surface mixing and sunlight
penetration in the absence of ice cover, etc. etc. Temperature change
is a very crude proxy for all of that and hence one that is best kept
as simple as possible.
Trevor Kenchington
Quoting Chris Harrod <[log in to unmask]>:
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> REPLIES WILL BE SENT TO THE FISH-SCI LIST
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>
> Folks
>
> A quick question. In many climate change projections, temperature
> changes are reported in °C shift from baseline, while precipitation
> (or discharge) is provided in % terms.
>
> What are peoples' thoughts regarding presenting temperature change
> as a % - as a means of highlighting those areas where changes are
> going to be large (e.g. Arctic). I appreciate that giving a °C value
> allows estimated of effects on vital rates etc.
>
> Cheers
> Chris
>
>
>> <> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><> ><>
> Professor Chris Harrod
> (Fish & Aquatic Ecology)
>
> Email: [log in to unmask]<mailto:[log in to unmask]>
> Twitter: @chris_harrod
> www.harrodlab.net<http://www.harrodlab.net>
> HarrodLab: Fish and Stable Isotope Ecology Laboratory
> Instituto de Ciencias Naturales Alexander von Humboldt,
> Universidad de Antofagasta,
> Avenida Angamos 601, Antofagasta, Chile
> Chile Mobile: +56 9 7399 7792
> Chile Office: +56 55 2637400
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