asked Her Majesty’s Government:

What has been the percentage increase in the carbon dioxide content of the atmosphere over the United Kingdom as a whole since the Second World War.

My Lords, my department has funded CO₂ measurements at Mace Head in the Republic of Ireland since 1987. There, the latest annual average is 385 parts per million, which is the same as that measured in Hawaii, where continuous measurements of carbon dioxide have been made since 1958. Carbon dioxide is well mixed in the atmosphere; therefore, the issues are comparable. The percentage increase from 1958 to today is approximately 22 per cent; that is, from 315 parts per million to 385 parts per million.

My Lords, I am grateful to the noble Lord for that reply. Is it not important to get these matters into proportion? Whatever may be the percentage increase over the period given by the noble Lord, does not the absolute figure remain microscopic? Is it not very difficult to believe that that microscopic figure is responsible for whatever global warming has taken place in recent years, particularly since, in very recent years, there appears to have been no global warming at all?

My Lords, the latter point is not correct. The averages may not have changed, but land temperature has increased considerably more than sea temperature because, in the Pacific, El Niño is a cooling factor—part of the ebb and flow. That has now switched off, as I said to my noble friend Lord Sheldon the other week. Therefore, the average can be very misleading.

An increase of 22 per cent, or of one-fifth—I earlier asked officials about this—in CO₂ since 1958, when measurements began in a consistent way by US scientists in Hawaii, is a considerable part of the problem. Of course, the figures I have given relate only to the Question and to CO₂. Figures for greenhouse gases are much higher, at 432 parts per million. All the evidence indicates that somehow we have to stabilise them at less than 500 parts per million; otherwise, we will not need to bother about future weather forecasts.

My Lords, knowing how well my noble friend briefs himself, I assume that he has now taken the opportunity to read the book written by the noble Lord, Lord Lawson. Even if he agrees only with part of it, like me, would he accept that making decisions on climate change, which are based on the assumption that forecasts for 50 years and 100 years are accurate, does not make a lot of sense to anyone, especially as it is very difficult to make forecasts for next week?

My Lords, my noble friend makes a point. No, I have not done the noble Lord, Lord Lawson, the justice of reading his book but, after the kind things he said about me a couple of weeks ago, I promise to make it a top priority. Leaving aside the forecasts for 100 years hence, let us look at the impact of what has already happened with greenhouse gas concentrations. Since 1900, the earth’s temperature has warmed by 0.8 degrees centigrade, much of which was in the past 50 years. Sea level has risen by 20 centimetres in the 20th century. The northern hemisphere’s snow cover has decreased in every month except November and December over recent decades. In the late 1980s, average snow cover dropped by 5 per cent. Arctic sea ice coverage has undergone long-term decline at all times of the year in recent decades. Last year, the extent of summer sea ice reached a record low. Those things have happened. They are not related to 100-year forecasts. Something is happening with the climate and the consensus says that we should be mindful and take some action.

My Lords, I am very grateful to the Minister for undertaking to read my book. It is short, and he will find it easy. Perhaps we may discuss it afterwards. But it really will not do to cherry-pick examples as he has done. Arctic sea ice, for example, has declined. Antarctic sea ice has increased over the past year by more than it has for many years. The average temperature is the average temperature, which he quotes when it suits him. He decries it when it does not. Does the Minister agree to look at this issue with an open mind and not perhaps be over-influenced by his department’s Chief Scientific Adviser, who is a very committed person in this dispute? In fact, there are scientists on both sides, and a substantial minority—30 per cent—disagree with the conventional wisdom.

My Lords, to be honest, I have not had discussions about the long term with the department’s Chief Scientific Adviser, a Nobel Peace Prize-winning scientist on this issue, who speaks for the majority of scientists, a point made by the noble Lord. The fact is that the figures I have given are those measured by earth-based stations. There are other ways of measuring what has happened with CO₂—in ice, for example, and using satellites, which are not so accurate. The fact of the matter is that concentrations of CO₂ are reckoned to have increased by 35 per cent since 1750, when the concentration stood at about 280 parts per million, and they are now higher than they have been for the past 800,000 years—I repeat, higher than for the past 800,000 years. It may be that in the ebb and flow of time CO₂ levels will go down again—in another 800,000 years—but we need to be able to do something today if something is happening to the atmosphere that is caused by man. That is the issue: is climate change man-made or not? The consensus is that it is.

My Lords, we agree strongly with the Minister’s and the Government’s sense of urgency over this matter. One of the big growth areas in recent years has been that of aviation and air travel. Could the Minister outline what the Government are urgently doing now to reduce those emissions, such as in the area of airport expansion?

My Lords, we are not going to be childish and stop people taking cheap holidays, which is what the Lib Dems want us to do. We cannot do anything as a nation on aircraft emissions; it has to be done internationally. The initial stage will be through the European Union. There is a plan for the Union to take on aircraft emissions as a whole in phase 3 of the emissions trading system, which will start from 2012. This cannot be done by individual countries; it has got to be done with international agreement. To start with, we have European-wide support from 2012. It is a very thorny issue and we agree with the noble Lord, but it cannot be done by one country alone.