All this, no doubt, caused some people to seriously think about climate change.

Whether or not the record temperatures are directly linked with greenhouse gas emissions, most scientists agree that climate change will make extreme weather more likely. Climate change was a crucial topic at the recent World Cities Summit in Singapore. It is one of the world’s biggest challenges. On one hand, population growth and rising standards of living are generating a bigger demand for energy, on the other there is a need to reduce greenhouse gas emissions. And cities are at the heart of the solution.

The global population is growing—from over 7 billion today, it will reach an estimated 10 billion by the end of the century. With this, the growth of cities will accelerate. Over half of the global population already lives in cities. By 2050, the proportion will be around three-quarters, with half of this growth happening in Asia alone.

Also, cities consume two-thirds of the energy the world produces; by 2040, they would use almost 80%. Even with heroic efficiency efforts, the amount of energy the world is consuming by the end of the century is likely to double compared to today.

One of the major challenges we face is how to halt the accumulation of greenhouse gases like carbon dioxide in the atmosphere?

The Shell Scenarios team—which has been developing possible visions of the future since the 1970s, helping generations of Shell leaders explore ways forward and make better decisions—models possible futures and has just published its latest supplement, A Better Life with a Healthy Planet: Pathways to Net Zero Emissions.

In it, we can see a possible path—challenging though it may be—to a world where emissions of carbon dioxide are at net zero levels. That means the emissions that remain are offset, or captured and stored below ground. This is not a target for Shell; it is something the world must achieve.

Cities, and how we plan them, will be central to achieving this. They have a huge opportunity to become more energy-efficient: through building standards; by using waste heat from power generation to warm homes; by encouraging high-density living to reduce travel and encourage smaller electric or hydrogen-powered cars; by building high-capacity public transport systems.

The evolving energy mix will be vital too. Natural gas, for example, produces half the carbon dioxide and one-tenth of the air pollution as compared to coal when burnt for power. Gas power stations also partner well with renewables, providing reliable electricity when there is no sun or wind. Here, adding carbon capture and storage (CCS) technology to power stations and industrial complexes will be critical to reduce emissions enough to reach net zero.

Renewables will, of course, continue to grow rapidly as part of the mix, but mainly produce electricity.

Today, electricity accounts for less than one-fifth of the total energy used in the world. For renewables to have a major impact, our scenario shows the share of electricity in the energy mix will need to grow to at least 50%.

This means people must meet the costs of, for example, electric or hydrogen-electric cars. Households and businesses not supplied with waste heat must be warmed with electricity. Food processing and light manufacturing must also go electric.

However, even with all these changes, the greenhouse gas emissions will continue to enter the atmosphere for the foreseeable future.

The production of chemicals used in so many of the things we take for granted will continue to rely on oil and gas. Where very high temperatures or dense energy storage are required—such as in the manufacturing of iron, steel and cement, or in heavy freight and air transport—we will almost certainly see continued use of hydrocarbon fuels.

There will also be regions that switch to low-carbon energy at different speeds, for political, economic or demographic reasons.

Continuing emissions will have to be offset. We can plant forests and use agricultural practices that raise the carbon content of the soil, such as ploughing partly burned biomass into fields. We can also burn biomass for power, coupled with CCS. Plants can suck carbon dioxide from the atmosphere. Using CCS will make sure it never goes back to the atmosphere.

Whether in cities or beyond, none of this will be easy. However, all of it is possible. Only if the world starts working towards it right now.