I’ve saved the worst for last.

In my previous two columns, we took a look at four of the five major worldwide problems cited in Daniel Callahan’s book, “The Five Horsemen of the Modern World,” featuring everything you need to know about climate change, food and water shortages, chronic illness, and obesity. Today we’ll tackle climate change and global warming.

“The last twenty years have been the warmest for thousands of years,” reports Callahan, “and 2014 was the warmest year since records began being kept in 1880.” It’s certainly been warm this year. You could step over the brook behind my house this summer, something I’ve never seen in the 38 years we’ve lived here. I’m especially concerned that we’re going to lose an entire year’s class of brook trout because they can’t get up into the brooks and streams to spawn.

“For hundreds of thousands of years,” noted Callahan, “carbon dioxide content of the atmosphere was below 290 parts per million, but by 2013 it had reached 400 PPM and is increasing at an average rate of 2 percent a year. The rate of increase in the twentieth century was ten times faster than in all the centuries since the last ice age. The year 2010 showed the biggest increase in CO2 emissions ever recorded, a 5.9 percent increase.”

Of particular concern here in our state, “ocean acidification is another consequence of carbon emissions, posing a threat to fisheries.” Maine has already experienced the problems of warming ocean water and acidification, with the collapse of our commercial fishing industry.

So, who is causing this global problem? “Industry currently accounts for nearly one-third of worldwide primary energy use and about one-quarter of carbon dioxide emissions, of which 30 percent comes from the iron and steel industry, 27 percent from non-metallic minerals (mainly cement) and 16 percent form chemicals and petrochemical production,” reports Callahan.

“The main sources of American emissions: electricity production (32 percent, more than 70 percent from burning fossil fuels); transportation (cars, trucks, 18 percent); industry (fossil fuels, 20 percent); commercial and residential buildings (10 percent); and agriculture (10 percent).

Sadly, a lot of Americans don’t think this is a problem, and that’s a problem! Callahan reported that “from 1990 to 2009 emissions in Russia and western Europe declined between 36 percent and 15 percent, while they increased by 206 percent in China, 244 percent in India, 172 percent in the Middle East, and 7 percent in the United States.

So, how do we solve this major problem, so our grandchildren and great-grandchildren do not suffer the consequences? “Solar power and wind power,” says Callahan, “with a track record and steady, incremental improvements, are more promising for use and deployment than speculative geoengineering ideas (such as the direct removal of CO2 from the atmosphere).”

Towards the end of the book, Callahan focuses on the potential for resolution of each of the five horsemen. First “there are few scenarios, even of a speculative kind about how (an increased and aging population) will be economically and socially managed.”

On global warming, he is both hopeful about technological advances and a strong increase in the public’s understanding of the problem, and pessimistic that we’re willing to take the steps to solve the problem. “The rapid introduction of renewables,” he says, “notably wind and solar power, is a hopeful sign, although still short of the needed financing…. Harm will be done. While the importance of adaptation is widely recognized it has so far only erratically been pursued.”

On food, he sees the greatest need “to be for strengthening food security, restoring recently weakened safety nets for afflicted countries, getting the leaders of poor countries to take food and agricultural research more seriously — and recognizing an ongoing need for financial help from wealthy countries to do that.” On water, “there is a wide range of ways to use water more efficiently, a number of technological means to lower water usage and to recycle it, and a number of possibilities for reducing water pollution.”

On chronic illness, he sees this as very difficult to deal with, partly “because the present health-care systems lack, and will continue to lack, adequate economic and other resources to manage it.” Finally, on obesity, which he says “is easily the disaster case of the five horsemen,” there are lots of solutions, “but none that have shown any progress of consequence.”

At the end of the book, Callahan focuses on two issues pertinent to each of the problems, and potentially a way to solve them: “the embrace of fear at the emotional level and the business community as a powerful participant with influence and considerable energy.” And he provides an impressive list of groups working to solve these problems.

He says “success is possible with the following approach: work diplomatically to gain the cooperation of industry, regardless of how obstructionist it has been in the past; intensify efforts to find technological pathways that work while also lowering prices; develop citizens’ groups at the local level and broader grassroots social movements to break through the barrier that too often succeeds in raising interest and concern but fails to generate action and legislative attention; if there are real dangers and hazards, do not hesitate to evoke them (but do not exaggerate); and , most of all, don’t give up.”

“The problems of the five horsemen are most likely chronic,” he concludes, “to be lived with and combatted simultaneously. That can be done.” Good to know!

George Smith is a writer and TV talk show host. He can be reached at 34 Blake Hill Road, Mount Vernon 04352, or georgesmithmaine@gmail.com. Read more of Smith’s writings at www.georgesmithmaine.com.