The vast majority of 'green-ness' of hosting is down to the source of the power - renewable v fossil fuel. The vast majority of DCs use grid power. Therefore (arguably) the best way to tell whether a DC is 'green' (at least in emissions terms) is to look at the emissions rates of the power grids in the DC's location.
The UK government publishes a set of country-based statistics for greenhouse gas emissions for companies to use when reporting their global emissions.
It doesn't go any more detailed than country so in some ways is rather unfair to some eg areas of US/Canada where the local utility is all hydro power but it's the best I've got! It also obviously doesn't cover those DCs who do genuinely generate their own local power (as opposed to buying green credits which is included in the figures as they are still using grid power).
It's a bit unwieldy, but you can get it at
http://www.defra.gov.uk/environment/...on-factors.htm.
I've extracted the following table from the long spreadsheet, it shows 2006 emissions by country (for those countries covered, and with some regional averages included). It would be interesting to see a comparable column for cost per kWh also.
kgCO2/kWh Country
1 0.00106 Iceland
2 0.00763 Norway
3 0.02792 Switzerland
4 0.04735 Sweden
5 0.09083 France
6 0.09593 Brazil
7 0.16315 Lithuania
8 0.19715 Latvia
9 0.20024 Canada
10 0.22800 Austria
11 0.23275 Latin America
12 0.24448 Slovak Republic
13 0.25417 Finland
14 0.27400 Belgium
15 0.33072 Luxembourg
16 0.33422 New Zealand
17 0.35419 Russian Federation
18 0.36293 Slovenia
19 0.36560 Croatia
20 0.37098 Hungary
21 0.38752 Spain
22 0.38819 Denmark
23 0.42730 Italy
24 0.42949 Netherlands
25 0.43066 Ukraine
26 0.43093 Germany
27 0.43927 Japan
28 0.45070 Portugal
29 0.50051 Philippines
30 0.51291 Romania
31 0.51434 Turkey
32 0.52836 Bulgaria
33 0.55209 Pakistan
34 0.55227 Korea, Republic of
35 0.55568 Thailand
36 0.56231 Egypt
37 0.56695 Singapore
38 0.58099 Ireland
39 0.59130 Non-OECD Europe
40 0.59239 Czech Republic
41 0.59990 United States
42 0.65684 Mexico
43 0.68425 Chinese Taipei
44 0.68454 Malaysia
45 0.71614 Poland
46 0.73000 Gibraltar
47 0.73326 Africa
48 0.74921 Estonia
49 0.77202 Indonesia
50 0.77932 Middle-East
51 0.78912 Cyprus
52 0.79728 Israel
53 0.80382 Greece
54 0.81894 Saudi Arabia
55 0.84284 China, People's Republic of
56 0.93596 South Africa
57 0.94321 Malta
58 0.95976 Hong Kong (China)
59 0.99646 Australia
60 1.28926 India