Philip Blanshard repeats a familiar fallacy, that carbon dioxide is OK because we breathe it out (Letters, July 3).

But we live in an age with many more creators of CO2 than absorbers. In the 1970s of which he wrote, the atmosphere was around 0.325% CO2, now it is 0.4%. One-fifth of all the carbon in the atmosphere was not part of the cycle 40 years ago, but was safely locked away.

Plants grow and absorb CO2. People eat plants and exhale CO2, which is absorbed by plants. As we have to grow all the food we eat, that part of the cycle must always be in balance. But we are digging up billions of tonnes of carbon and burning it for fuel far faster than nature produced it. At least burning gas produces more energy for a given amount of carbon dioxide emitted, but it is still being produced faster than nature can absorb it.

It is not enough just to plant trees, because mature trees reach a point where they stop absorbing CO2. Dead trees decay and return much of the carbon to the atmosphere, and relatively little is locked in the soil. To use trees to soak up the extra carbon, we must actively harvest them and prevent them from releasing this absorbed carbon. The solution would be to bury them deep enough that they do not decay and leak carbon dioxide. Abandoned mineshafts would be ideal, and certainly easier than trying to stuff them down oil wells.

But how can it possibly be sensible to dig highly concentrated carbon in the form of coal or oil from deep underground, then try to replace the carbon by growing billions of tonnes of trees just to send it to landfill, especially as we would need to bury a significantly larger volume of trees than we mine coal? Why not just leave the coal in the ground?

Alan Ritchie, 72 Waverley Street, Glasgow.

We are never going to lead the world on climate change ("Credible plan will put us at forefront of positive action on climate change", The Herald, July 5). Our government is not being watched to see if it will follow through on its climate change Act. All our renewables activity has no appreciable effect on global emissions. We can continue to plaster our land with wind turbines, but that affects only us (often adversely, unfortunately). South Africa reportedly is on the way to building a 4000+ MW coal-fired power station, and Germany – even while going for offshore wind – is reportedly planning a host of coal plants too. Other countries are doing the same – having massive fossil fuel electricity generation, even if renewables are progressing too.

Nuclear is still in favour – even if we reject it. The fundamental reason for renewables in the UK has to be the saving on imported energy, but of course we should also press for an international cut-back in warming emissions. Let's put our weight behind CCS (carbon capture storage) development, even as Norway moves to a pilot system ahead of our abandoned proposals.

Joe Darby,

Glenburn, St Martins Mill,

Cullicudden, Dingwall.