Very few readers of this newspaper will have any doubt concerning the link between smoking and cancer.

The scientific evidence is undisputable.

Action has been taken, and many lives have been saved as a result. Yet, while the medical evidence was for long overwhelmingly accepted, powerful interests in the tobacco industry fought a rear-guard action to frustrate efforts to discourage new smokers from buying their products. Their tactic was simple: sow the seeds of uncertainty in the public mind and play for time.

I was reminded of these tactics by the recent article by former editor Matt Dempsey in this newspaper in which he reported on a closed meeting in Dublin addressed by climate sceptic Richard Lindzen. As with many climate sceptics, Lindzen has ‘‘previous’’ experience with the tobacco industry, acting in the past as one of their witnesses as they battled through the courts to maintain business as usual.

Which of us would act today to encourage one of our family to start smoking on the strength of such an opinion which flies in the face of well-established scientific research? But the precautionary principle applies to climate change just as much as it does to smoking.

Tactic

The tactic of emphasising uncertainty as justification for inaction was transferred from tobacco to the climate change arena by individuals who saw the writing on the wall for the tobacco industry. What changed was the source of funding.

Large oil and coal companies were only too willing to pump funds into organisations willing to deny the link between greenhouse gas emissions and climate change.

Sadly, Dempsey, and several individuals at the meeting referred to above, seemed happy to take the bait and I consider it would be an injustice to Irish farmers not to redress the flawed arguments presented.

Irish farmers are sensible and responsible people who, more than most, are acutely aware of the changes in climate taking place around them. They know the growing season has changed and that they will have to adapt to changes in climate currently ongoing. They also know in their hearts that no one can argue with a thermometer that says everywhere in Ireland is half a degree warmer than when their parents were farming 30 years ago.

It would be nice if methane was not a significant contribution to greenhouse warming, and Lindzen’s message is clearly music to the ears of those who seek the huge expansion of dairy cattle. But, in reality, just as with tobacco, the evidence is incontrovertible. Methane was considered to have a warming effect 25 times greater than the same amount of carbon dioxide up until a decade ago, measured over a timescale of a century.

More recently, the governments of the world have now signed off on a new figure of 34 times greater than CO2.

Indeed, if a 20-year time span is chosen, this figure increases to 86 times greater. No amount of spurious comparisons with other gases such as water vapour can disguise the seriousness of agricultural emissions as drivers of climate change.

Of course, it is difficult to look with certainty into the future course of climate, and natural variations. From year to year and decade to decade, noise can be introduced into any trend. But those who seek to cherry-pick start and finish dates to prove that models don’t work will, I am sure, not succeed in confusing most Irish farmers.

The fact is that when natural variability is taken into account, models estimate well the 10- to 15-year observed trends over the past half-century. If anything, they tend to be overconservative.

Certainly, nature is sending a signal that things are happening quicker than the models projected.

What, I wonder, is causing the sea level rise to accelerate, or the Greenland and the Antarctic ice cap to contribute over 360bn tonnes of meltwater to the oceans every year over the past decade, six times higher than over the previous decade? Why do thousands of thermometers show that the world has warmed by 1.1°C since pre-industrial times?

In Ireland, we have to come to terms with these realities and the fact that we emit more greenhouse gases than the 400m poorest people on earth.

In terms of responsibility, we also have to deal with the hard fact that agriculture currently contributes over one-third of the national total and projects no decrease in emissions for the next decade.

Demonising almost all climate scientists and individual civil society groups as alarmists ill-befits those who seek to lead Irish agriculture.

I have nothing but admiration for the way in which most Irish farmers steward the landscape.

They deserve to be told the truth on climate change and deserve better leadership to cope with its implications.