SCIENTISTS HAVE KNOWN about the greenhouse effect and feedback loops for almost two hundred years, but it wasn’t until the 1970s that the extent to which these phenomena were affecting global climate really started to sink in. By the mid-1980s, many scientists were warning that burning fossil fuels and pumping massive amounts of greenhouse gases such as carbon dioxide into the atmosphere were causing global average temperature to rise at a steady and alarming rate. In 1988, the World Meteorological Organization and United Nations Environment Programme established the Intergovernmental Panel on Climate Change to bring scientists from around the world together to examine the science and present results to government representatives. After the IPCC’s First Assessment Report in 1990, and a supplemental report in 1992, the United Nations Framework Convention on Climate Change was established at the 1992 Earth Summit, or United Nations Conference on Environment and Development, in Rio de Janeiro, Brazil.

      Subsequent international conferences were held and assessment reports were released in 1995, 2001, 2007, and 2014—each one providing stronger evidence for the human role in global warming and offering greater evidence of its potential disastrous consequences.

      By the time world leaders signed the Paris Agreement in late 2015, based on the 2014 Fifth Assessment Report, there was no denying that humanity was facing a serious crisis, in large part of its own making.

      As the scientific evidence for human-caused climate change has become more robust, our understanding of the consequences has grown. Using increasingly sophisticated computer models, tree ring and ice core samples, historical records, satellite data, observation, and other methods, scientists from a range of disciplines worldwide have examined global warming’s current and potential impacts on everything from oceans to weather to agriculture to human health and beyond. It’s not a pretty picture.

      But just as our understanding of global warming and its consequences has grown, so too have the various solutions that we must employ to confront this great challenge. We know that we must cut down on and eventually stop burning fossil fuels for energy. That means shifting to cleaner, renewable energy sources such as solar, wind, and geothermal. We also know that we have to protect and restore green spaces, such as forests and wetlands, that absorb and sequester carbon and keep it from the atmosphere. And we have to look at agricultural practices and diets that contribute to climate change. The good news is that renewable energy technologies have been improving by leaps and bounds, with storage and grid systems making power from wind and sun increasingly viable. Awareness of how our own daily habits contribute to climate change and other environmental problems is also growing, leading many people to make changes that collectively add up to much-needed improvements.

      If we understand the problem, have so much evidence for the catastrophic consequences that await us if we fail to address it, and have many solutions at hand, why are we so slow to address the crisis in a meaningful way? The 2015 Paris Agreement was a positive leap forward, but even it won’t prevent the global temperatures from warming beyond the necessary threshold of 2 degrees Celsius (3.6 degrees Fahrenheit) over preindustrial levels, let alone the agreement’s aspirational goal of 1.5 degrees Celsius (4.2 degrees Fahrenheit). Many experts believe that even if all countries that signed the agreement meet their stated targets on time, global average temperatures will rise by 2.7 to 3.5 degrees Celsius (4.8 to 6.3 degrees Fahrenheit)—which scientists agree would be catastrophic for humans and numerous other species.

      The complexity of the problem is a major barrier to resolving it. Because we have waited so long to address global warming, and because the CO₂ we’ve already emitted into the atmosphere will stay there for a long time, avoiding the worst impacts will require major changes in global governance, economic systems, and personal lifestyles. That needn’t be bad. Addressing the challenge of climate change could have other benefits, such as reducing inequality, improving health and quality of life, sparking innovation, and creating jobs. But we need a paradigm shift in our economic thinking—which isn’t as difficult as it might sound, if it’s put into context. We’ve changed economic systems many times when they no longer met our collective needs or when they were seen to do more harm than good. But politicians and the people they are supposed to represent often resist change when it’s easier to continue business as usual—especially when the success of politicians often depends on setting plans according to shortterm election-cycle timelines rather than seeing the long-term big picture.

      But complexity isn’t the only barrier. The fossil fuel industry has become entrenched in all aspects of life globally, with massive infrastructure to support it. It’s also the most profitable industry in history. It’s no surprise, then, that people who profit from the exploitation of coal, oil, and gas would do what they can to protect their interests, even to the detriment of human health and life. Studies have shown that people in these companies have long known about climate change and its possible consequences but have done everything they can to downplay the problem, even spending large amounts of money and time on campaigns designed to sow doubt and confusion regarding the scientific evidence. Large power companies also see their interests threatened by distributed energy systems that can be employed at the household or community level.

      The fact that wealthy industrialized nations have caused much of the problem while those that are starting to catch up want some of the same benefits also presents a barrier to progress. As countries with large populations such as China and India demand the same levels of comfort that fossil fuel use has conferred on wealthy industrialized nations, emissions increase. International trade deals that prioritize corporate profits over environmental protection and national interests also contribute to the worsening crisis.

      The challenges and barriers are formidable but not insurmountable. Solutions are available, but often the political will to implement them doesn’t match the urgency of the situation. With extremely powerful, wealthy, vocal opponents arguing that there is no problem, or that we needn’t do anything about it if there is, many people are understandably confused, and progress is slowed or stalled. The following three chapters will examine what the evolving science and its history tells us about the increasing consequences of climate change, and explores many of the barriers to resolving the crisis.