Don't be so sure of that. The issue with nothing ... you are saying UK has _no_ emissions at all? Very doubtful.The UK could disappear tomorrow and from a climate standpoint, nothing would improve. The entirety of England, Scotland, and Ireland could sink into the ocean and it would not affect Climate Change in any way.
85% of CO2 emissions are in BRICS countries.
Also with the UK disappearing, all imports the UK does from BRICS would disappear. And with that probably at least some reasons for these emissions that are currently attributed to BRICS.
Very easy example to make this clearer:
If leather was only produced in China, all the chemicals used for tanning and the associated environmental impact would be attributed to China alone. So you could say that eg UK has no impact on waste stemming from tanning chemicals.
However, if the UK is importing 5% of the leather, in fact the UK is _responsible_ for 5% of the environmental impact, and with the UK disappearing tomorrow, like you say, it would indeed have a considerable impact on chemical waste from leather tanning, although the UK does not use these chemicals at all.