Has the cold weather caused the nation's carbon emissions to go up?

As the country reaches for the heating controls, have our carbon emissions increased even if fewer of us are driving?
Leo Hickman
guardian.co.uk, Monday 18 January 2010 10.04 GMT
Has the UK's cold snap caused the nation's carbon emissions to go up or down?
C Dyer, by email
As ever, many thanks for the responses posted so far. Unsurprisingly, perhaps, the general consensus seems to be that the UK's carbon emissions must have gone up over the past month or so due to the cold snap. I think it's a given that emissions created as a result of domestic heating must have gone up significantly, but there still seems to be a question mark over just how much a reduction in road traffic might have acted to ameliorate this impact.
The Department for Energy and Climate Change has told me that it doesn't monitor overall national emissions on a daily or even a monthly timescale. The only figures it has are annual national emissions which aren't much use to us here.
Thanks to the National Grid link provided by jayb, we can see overall gas demand in the UK running well above the seasonal average for this time of year. National Grid has also provided this graph to show gas demand since last October, set against expected demand during both warm and cold spells.Electricity demand also shows an above-seasonal rise over the past month, but not as much as gas. A National Grid spokesman told me:
Between 14 December 2009 and 14 January 2010 inclusive, we would have expected the electricity usage on normal (a 30-year average) weather to be 30.6 TWh (terawatt hours). The outturn was 32.5 TWh which is an increase of 6.3% over normal (1.9 TWh).
The temperature differential on average at 12:00hrs was 4.45C less than our temperature lagged normal of 5.1C.
This averages out over the whole period as an extra five large generation units (assuming each unit is 500MW) running continuously across the 32 days or the equivalent of one very large power station (2.5GWs) running all the time for the period.
Jam0boggins also makes an interesting point about the carbon intensity of electricity generation over this period:
The surge in gas demand has also (I believe) led to more electricity being generated through coal. Our website http://www.realtimecarbon.org/ has shown that the carbon intensity of electricity increased over the period. Also, people will likely have been putting electric heaters on in addition to their normal central heating. People staying at home instead of going to work will probably have meant that both the offices and houses would be heated/lit, so also causing an increase.
Ambodach makes a similar - and very interesting - point about the windless conditions meaning that there is a strong possibility that our becalmed wind turbines would lead to more coal being used to generate electricity.
Attempts to get a figure for transport-related emissions have proved elusive, though. As tomthetortoise implies, there's not that much value trying to make a calculation based on the combined distance travelled by the UK's motorists during the cold snap because driving at slower speeds can sometimes produce more in the way of emissions. A better indicator would seem to be to compare the amount of petroleum consumed over the past month to the seasonal average. Sadly, according to the UK Petroleum Industry Association (UKPIA), no figures exist - yet, at least. The best it can offer at present is a monthly breakdown of last year's consumption. But it urges caution about reading too much into the figures because petroleum use has fallen over the past year due to the recession. A spokesman said:
Given the weather conditions over the last weeks, we would expect overall retail fuel demand to have fallen - people not able to drive to work or on business; social trips cancelled/postponed etc. Commercial road transport fuel demand may prove to be affected temporarily due to deferral of deliveries, but likely to be made up as conditions return to normal. In any event, overall road fuel demand in 2009 was down 4-5% against 2008 because of the recession; petrol demand has been in steady decline since the peak of 1990 (about 30% lower in 2008 against 1990).
There is one curious anomaly in the figures from last year, though, that the UKPIA agrees might indicate how much petroleum use can drop off during a cold snap. There is a noticeable drop in the figure for March 2009 which the UKPIA says covers the less severe cold snap experienced last winter during February. It shows a reduction in consumption of about 13% compared to the February and April totals.
Until some harder figures are published in coming months, I think we'll have to settle for an educated guess when it comes to answering this particular query. However, policywonking makes a good point:
Will we have a similar question when we have an unseasonably warm snap? Point of averages is that if we have a period of below average temperatures we are likely over time to have a period of above average temperatures, too.
This reminds me of something I read years ago, which noted that Washington DC was the first city in the US to use more electricity during the summer than in the winter due to the rapid and widespread adoption of air conditioning units once they became affordable for domestic use.
On 11 January Leo originally wrote:
There's a temptation to immediately assume that emissions must have gone up during the freezing conditions as shivering folk around the country reach for the heating controls, or switch on the kettle to fill a hot water bottle. In fact, the National Grid has been reporting record surges in demand. But what about the reduction in road traffic over the same period? Does our reduction in mobility cancel out the heating-related emissions?