To the editor:

This is in response to two letters appearing on July 19 questioning man-made global warming. The allegations against the International Panel on Climate Change have proved to be bogus and the skeptics mentioned are relatively unknown. In fact, I would be interested in who they work for.

Here are some established and fully verifiable facts.  During the last ice age, ending about 10,000 years ago, temperatures were only 9 degrees cooler.

Key changes already observed here in Massachusetts:

Temperature has risen 2.9 degrees since 1895.

Growing season has expanded 11 days since 1950.

Sea level has risen 11 inches since 1922.

Strong storms have increased 55% since 1958.

More established facts:

Carbon dioxide traps solar-generated heat.

Over the last 800,000 years, there has been a natural carbon dioxide change of 100 parts per million that normally occurs over 5,000 to 20,000 years. The recent increase of 100 ppm has taken only 120 years since the Industrial Revolution had spread the burning of fossil fuels worldwide.

These effects are accelerating due to an engineering term called positive feedback, of which there are a number of examples. One is Arctic sea ice. As it progresses from a reflective surface to open water, more heat is absorbed by the water. This is like an engine where part of the output is fed back into the input so that it runs faster and faster.

These facts are so disturbing, there will always be those who refuse to accept them, especially since they are human-caused as a result of the Industrial Revolution and the burning of fossil fuels. My favorite analogy is from my profession. If nine out of 10 engineers proclaim a bridge is in danger of collapse with only one dissenter, I think we would all agree we would close the bridge and fix it to avoid a likely disaster.

It is not too late to avoid the worst consequences but it is going to take fast action on the personal, state, national level.

The underlying driver of global warming is the relentless increase in population and consumption with the poorer developing world aspiring to consume like us. Such aspirations will not be possible for various reasons. But what we will see, long term, is human migration that will make today’s migration into Europe and North America look very small by comparison.

It is hard to predict when but probably within 20 to 40 years we will start to see flooding of seacoast cities, crop failures in the tropics and diminished ocean fisheries. Just last week, our government predicted declining U.S. corn and soybean production and higher prices in the near future because these crops are heat sensitive.

We will be seeing internal migration as our cities and low-lying Southeast and Gulf coasts are inundated. This will coincide with a mass movement of people from South Asia, Africa and the Americas to Europe and North America.

Our current border problems seem small by comparison, but it is time to take population migration out of politics and get it under control before we are overwhelmed by it in the future.

Of course, we understand and sympathize with people wanting to escape extreme poverty, gangs and murder with dysfunctional governments and their treatment at our border. Polls taken some years ago, before conditions got as bad as they are now, asked Latin Americans where they would like to live if given the chance. Some said Spain but the large majority said the United States.

We are beginning to see a change in the liberal media. Atlantic.com and the Washington Post recently raised the question about the many hundreds of millions of people in the rest of the world who live similar or worse conditions.

Europe, Canada and especially the U.S. of A. have the technology and relative wealth to make the world livable. But we can’t do it if we are swamped and become dysfunctional ourselves. Look at the strong rise of far-right parties in Europe that threaten political stability there caused, at least in part, by recent migration from Afghanistan, Africa and, of course, Syria.

Looking at the big picture and the more distant future, there are three things we must start doing now:

Eliminate fossil fuels.

Increase foreign aid starting with Central America.

Reform our migration policy to bring it under control before it is too late.

George P. Smith

Manchester