Editor’s note:

What will the future look like?

Will the earth be overwhelmed by climate change?

Will economic growth fall victim to rising temperatures and resulting natural calamities?

These questions, and more, are answered by Jorgen Randers, professor at the Norwegian Business School and author of “2052: A Global Forecast for the Next Forty Years,” published last year. He is best known as the coauthor of the seminal 1972 book “Limits to Growth.” Randers talks to Shanghai Daily reporter Ni Tao in an e-mail interview.

Q: What motivated you to write “2052” on the 40th anniversary of “Limits to Growth”?

A: I spent the 40 years between then and now trying to save the world from global unsustainability, with limited success, and I had become very curious about what will actually happen over the next 40 years.

So I decided to try to find out, and “2052” contains the result.

“Limits to Growth” and its follow-up studies were scenario analyses describing a number of different futures, discussing their relative merit, and recommending policy that would make the future more sustainable.

“2052” is a significant deviation from that: it simply states what I believe will happen, on a broad scale, between now and 2052.

The forecast is driven by a computer model, but also tempered by my best guess at how human decision making will play out over the coming years.

I have been worrying about the future for decades, and I wrote this book for peace of mind. The future I found is not the future I would hope for, but knowing what lies ahead does give me peace of mind.

Q: How will climate change affect global food security?

A: The increased level of CO2 in the atmosphere accelerates plant growth; photosynthesis speeds up when there is more CO2 around.

So if this were the only effect of man-made CO2 emissions, the effect on food growth would be positive.

The total effect on global agricultural yields will be limited over the next 30 years, but then yields will start to decline because the heat effect will overwhelm the CO2 effect.

There will be huge regional variation, and exactly how agriculture will be affected in a specific locality is not yet known by science.

There is speculation that corn in the United States and wheat in India may suffer most.

But farmers will change to other crops in response — and when there is nothing else around, consumers will have to adjust their tastes to the new stuff.

In sum I believe that the world will be able to supply the food that is demanded in 2052.

The problem will be then, as now, that many people will starve because they cannot afford to pay for the food they need.

Q: What makes it so hard to adopt renewable energies if they are technically feasible and economically inexpensive?

A: In principle it is simple to solve the climate problem.

To stop the temperature from rising, we need to halve man-made greenhouse gas emissions by 2050.

This cut can be achieved easily with known technologies and at a surprisingly low cost. Solving the climate problem would cost only a couple of percent of the GDP.

The problem is that global society appears to be unable to make the decision to act.

Why?

Because acting would mean moving from the current, well-tested, and cheap solutions (like coal-based power and cars running on gasoline) to more expensive solutions (like wind and solar power, or coal and gas with carbon capture and storage).

Neither the voter, the politician, nor the capital markets are much in favor of moving from a cheap to a more costly solution.

Therefore it does not happen, at least not quickly.

Q: Does political system matter in responding to climate change?

A: Yes it does.

What we need is a system of governance that puts more emphasis on the interest of our children and grandchildren — that is, on future generations.

We need stronger government that can force us all to be more long-term in our current action.

I believe the current Chinese government has many of the desirable characteristics in this context: it is seeking to allocate capital in ways that bolster the long-term future of China, even when this means lower growth in disposable income.

Q: You say in the book we are “overshooting” the earth’s resources. How much longer can we continue to overshoot?

A: Humanity has already overshot a number of limits, and in some cases we will see local collapse before 2052.

One example is the likely loss of coral reefs, another is the likely loss of the tuna.

But the most worrisome overshoot is that caused by our ongoing overshoot in climate gas emissions — one approaching global collapse.

We are emitting twice as much greenhouse gases every year as is being absorbed by the world’s forests and oceans.

This overshoot will worsen and not peak until 2030 in my forecast.

Only then will humanity begin to reduce its annual global emissions — because only then will the ongoing human effort to reduce energy use per unit of GDP and the carbon emissions per unit of energy be so successful that global emissions will go down in spite of continued growth in GDP.

The effect of this overshoot will be a significant increase of CO2 in the atmosphere, with consequent warming.

Some will be surprised that I do not think humanity will overshoot conventional resource limits — for example oil, food, water — by 2052.

The main reason is that I believe the human economy will grow much more slowly than most people think.

Hence we will have better time to evolve substitutes for scarce resources. The lower-than-expected GDP means lower use of resources.

Q: You paint a very different picture of megacities of the future. How will they look?

A: Already 50 percent of us (3.5 billion) live in cities.

By 2050 70 percent (5 billion) of us will. So, almost all the population growth from now to 2050 will end up in cities.

Many cities will be very big — twenty million people and more. Some will be well managed, many will not.

People’s daily life will be strongly influenced by the ever-present Internet and fantastic virtual entertainment.

There will be sinking political interest in the rural parts of the country and in undisturbed nature.

The well-managed cities will provide improved protection against climate change for its citizens, compared to the raw exposure to calamities by people in countryside.

Q: Are you optimistic or pessimistic about the future? What do you see as the greatest threat to humanity?

A: I am afraid that humanity will decide to create a future for itself that is much less attractive than what could have been achieved if we decided to run the world according to rational policy.

But pessimism is not the best description of my feelings.

The best description is sadness: I am sad because global society is likely to make a number of wrong judgments and decisions in the decades ahead. And as a result it will willfully create an unattractive future world.

Our greatest threat is self-reinforcing climate change, and the greatest downside in our future is brought on by increased warming up to 2052 that will lead to runaway climate change in the second half of the century.

But it really does not matter how I feel — optimistic or pessimistic, happy or sad.

What matters is that the conclusion to be drawn from the 2052 forecast is simple and straightforward.