The Intergovernmental Panel on Climate Change (IPCC) released a shocking report “Global Warming of 1.5°C.” An equally accurate but more evocative title could have been “We’re almost out of time.”
It is shocking, not because those working on the science are surprised by the messages (indeed they are all based on existing and published science), but because in aggregate the message is extraordinary and alarming. The diversity and severity of impacts from climate change read like a narrative we might see in a Hollywood movie, but are in fact, and disconcertingly, the clear-eyed projections of where we are heading in reality, barring massive economic mobilization and rapid transition to cleaner technologies.
To provide the first point of context, most people are familiar with the fact that the earth has gone through ice age cycles. During the depths of the last ice age, Chicago was under about half a mile of ice. The difference in global average surface temperature between the depths of the last ice age and today is around 4 to 7 degrees Celsius. While projecting “where we are heading” is complicated, it’s fair to say that the momentum of our global economic system is hurtling us toward warming the planet by 3 to 4 degrees—in other words, a climate shift not that different between the last ice age and today.
The new report focuses on what impacts we might expect from even half of that warming, at 1.5 degrees and 2 degrees, and the remarkable story is even at these lowest levels of climate change that we believe are achievable—given that we’ve already warmed about 1 degree—the impacts are significant and quickly become severe as temperatures reach beyond 1.5 degrees. Other sources, including this interactive graphic and the report summary, detail some of the headline numbers and I will not catalog all of them here. Notable is the likelihood that going from 1.5 to 2 degrees would expose several hundred million people dangerous climate-related risks by 2050, and would likely wipe out 99 percent of coral reefs. And the scale of the challenge to retool the economy on a short timeline is staggering: the study estimates that global emissions of greenhouse gases need to drop by 45 percent from 2010 levels by 2030 to stay on a 1.5 degrees path. Given dramatic recent increases in emissions, is equivalent to a roughly 60 percent drop from today’s levels, in 12 years.
How risks increase with temperature, and why 1.5?
While the headline numbers matter profoundly, so does the fact that this report addresses a fundamental question: How much risk does climate change pose to us as we dial up global temperatures? In other words, as we continue to load nearly 50 billion tons of CO2 equivalent and other climate-changing substances into the atmosphere each year? Will we reach a tipping point?
The report dives into this question in a structured and specific way. First, it looks at impacts of some specific levels of climate change—assessing impacts specifically at 1.5 and 2.0 degrees warming above pre-industrial levels, but also looking at a broader spectrum of possible warming outcomes. It then aggregates and synthesizes what we know from previously published scientific, peer-reviewed, and otherwise vetted literature on how these warming outcomes would affect ecosystems, sea level rise, human health, livelihoods, communities, and more. An important and central aspect of this exercise was to better communicate how each of these risks changes with increasing temperature, asking questions like, “How much more would heavy rainfall events happen in a world of 1.5 degrees warming compared to today, and how much more severe would things get if warming increased to 2 degrees or beyond?”
It’s worth pausing to understand the seemingly odd concept of “1.5 degrees” which gives the report its title. Why 1.5? The origins are in the original international treaty on climate change, the 1992 Framework Convention on Climate Change. This treaty (which was negotiated under the George H.W. Bush administration), recognized the importance of climate change and set up a process for the international community to begin to address it. The core principle of the international approach to climate, formally embedded in that agreement, was “to avoid dangerous anthropogenic interference in the climate system.”
It was left to future science and policy discussions to work out what exactly “dangerous” means. In any case, what eventually emerged is a consensus on the need to understand how risks of climate change increase as temperatures rise. As these discussions unfolded, it also became clear that different kinds of risks—such as sea level rise, risks to ecosystems, risks of tipping points, and risks to human systems—could have slightly different sensitivities to global warming, and thus such concepts were disaggregated and evaluated separately.
The resulting concept was graphically depicted in a now well-known figure from the IPCC Third Assessment Report in 2001. While formally titled “Reasons for Concern,” the vivid yellow, orange and red colors on the figure earned it the nickname of the “Burning Embers diagram.” It went through several refinements as new science was developed, but was importantly the foundation for a discussion across government and civil society to narrow in on a more formal definition of dangerous. Based on the understanding at that time of risks, the uncertainties, and potential impacts, this discussion increasingly cohered around the concept that there appeared to be more extreme and significantly worrying risks—across all of the categories—beyond about 2 degrees of warming. By the time of the Copenhagen U.N. Climate Change Conference in 2009, the international community formally adopted keeping warming to under 2 degrees.
Yet even as the consensus for 2 degrees was crystallizing, questions arose about whether the 2 degrees goal might be too high. On the one hand, additional published science bolstered confidence in impacts at lower warming levels, and indicated the possibility that impacts might be more broad and severe than originally thought. In addition, discussions in the broader international community grappled more directly (if not completely) with issues of equity and ethics and how those ought to relate to this core risk assessment. It’s a fascinating and important story, but the upshot was an was an embedding of a 1.5 degree goal at the beginning of the landmark 2015 Paris Agreement: “Holding the increase in the global average temperature to well below 2 degrees above pre-industrial levels and pursuing efforts to limit the temperature increase to 1.5 degrees above pre-industrial levels.” As a direct result of the Paris Agreement, the international scientific body of the IPCC was asked to evaluate and report on our understanding of the difference between 1.5 degrees and 2 degrees, and what it would take to get onto a global path to keep warming under 1.5 degrees.
That is where the new IPCC report comes in. The report evaluates both quantitatively and qualitatively how much the risks rise as temperature increases. The short answer to these questions in the report is something like this: We’re already at 1 degree warming and seeing some significant impacts; 1.5 degrees is going to have more severe impacts; 2 degrees has more; and we probably don’t want to test what happens above 2 degrees—although our current momentum appears to have us on a trajectory for about a 3 degrees or more world.
In the new report, the updated Reasons for Concern figure shows a broad feature of increasing risks above 1.5 degrees across both the five reasons at the top and the new, even more disaggregated system assessments on the bottom row. Beyond the diagram, the report offers plenty of granular detail, for example, estimating how much additional habitat would be lost when moving from 1.5 to 2 degrees, or how many more ice-free summers the Arctic would have. Some of them are surprisingly sharp increases for half a degree—such as the estimate that the percent of global population exposed to extreme heat at least once every five years rises from 14 percent to 37 percent, or the estimate that coral reefs would degrade “only” an additional 70-90 percent under 1.5 degrees but 99 percent in a 2 degrees world. These are sobering because 2 degrees itself remains a hard-to-achieve goal and warming beyond 2 degrees would have even greater consequences. I won’t exhaustively detail the other impacts as they have been centrally featured in much coverage of the report, so refer you to those sources or to the report itself.
Pathways to manage risks: Can we keep under 1.5 degrees?
While it is vital to understand the risks with different levels of warming, an equally urgent question is whether and how the planet can get onto an emissions trajectory that would keep on a 2 degrees or, if at all possible, a 1.5 degrees path. There are a few key aspects of this challenge: a dramatic retooling of the global production and consumption toward low or zero greenhouse gas approaches by roughly 2030; a likely build out of untested carbon removal technologies at large scales toward mid-century; and widespread measures to adapt to climate change.
The IPCC report illustrates several approaches that could achieve 1.5 degrees with limited “overshoot” (i.e., going above 1.5 and then back down). Coal power would have to drop by 60-80 percent from 2010 levels by 2030. Renewable energy sources would grow by roughly 100-500 percent, reaching about half of total global electricity generation by 2030 (again, 12 years from now), and 70-90 percent by 2050. These features and others are laid out in detail in the information-rich figure below. The overall message is that the math can actually work, but the mechanism for realizing such rapid and dramatic transformations is, well, just not part of the report, and of course is the biggest question of all. In other words, the report tells us that these pathways are physically and technologically possible, but it is up to us to figure out what social and political approaches we have to take to implement those pathways.
So, the answer of “can we do it” is yes, technically. But if we are to do it, how can we do so? Clearly the problem is massive. Such large and complex problems certainly require transformational thinking, integration, and big movements. But tackling this problem will also require progress on myriad smaller and manageable elements.
The scale and speed of the technological transition is extraordinary but plausible. For example, individual technologies have undergone rapid transitions before. The first iPhone was revealed only 11 years ago—there was no such thing as an app in early 2007. Automobiles went from less than 1 percent of road vehicles in the United States in 1900 to nearly 100 percent thirty years later. While some technologies do not lend themselves to rapid replacement, the general principle is that relatively rapid transformational change is feasible in many applications. In addition, the IPCC report notes that, while the scale and duration of mobilization is unprecedented, the speed of mobilization is not, recalling the efforts in the United States to mobilize for World War II.
The social organizing (or political) challenge—how we collectively change behavior and make dramatically different choices—is the most daunting. There are certainly many reasons to be pessimistic about our collective ability to drive broad and significant change, for example, if we frame the problem around concepts like convincing voters (or politicians) to invest now for a future payoff. And national level leadership in some key countries—the U.S., Australia, and perhaps soon Brazil—is driving against climate action. Nevertheless, a few alternate framings can be helpful:
- Economic Growth. Many studies have pointed out the economic growth benefits that accrue from such transitions. Clean energy provides jobs and in many cases more jobs than dirtier technologies. Clean air and a green environment are healthier for people. The recent New Climate Economy report estimated that a widespread, full investment in a clean economy transition would lead to a net $26 trillion in benefits by 2030.
- Innovation. Technology is a real part of the solution to climate change, and we have developed a global innovation infrastructure that is by any standard impressive. Many of our best and brightest are inspired to work on new energy and climate-friendly technologies and institutional approaches. Refocusing on building this technological innovation apparatus, educating students globally in relevant fields, providing the right structure for early stage financing, and bringing these technologies to market is a core part of the solution.
- We are on a path. This pathway is not new, and we have already begun the transition. Renewable energy deployment has shown remarkable progress, surpassing expectations and surprising analysts. Since 2012, more than half of new electricity power additions have been renewables. The cost of solar has fallen over 70 percent since 2010 and combined renewable costs are falling so rapidly that they are expected to be competitive or cheaper than fossil fuels by 2020. So, progress is already happening, in clean energy and many other areas relating to climate stabilization—it’s just that we need to go faster and do more, which requires choices and policy.
- All Hands. The only strategy that works is one that fully engages all levels of action, which includes personal actions but also includes policy and decisionmaking in all other communities and groups: cities, towns, counties, states, countries; places of work; businesses and investors; universities; communities of faith, and more. Each of these has ways they can address the issue. One recent example of this is here in the U.S., where a coalition of over 3,500 cities, states, businesses, and more, have recommitted to doing their part to achieving the goals of the Paris Agreement. A recent study that I helped lead indicated that this coalition, representing over 50 percent of the U.S. population, nearly 60 percent of U.S. GDP, and equivalent to the world’s third largest economy—could drive U.S. emissions down by roughly 24 percent by 2025 relative to 2005 levels. Such engagement, while not yet enough, can help build the groundwork for the accelerated ambition that the report calls for. And it underscores that elections and political choices will matter greatly over coming years in the United States and globally.
The IPCC report crystallizes what we already knew about the risks of climate change and throws the challenge into stark relief. The scale and speed of transformation will require not just new technologies but innovation on new models to organize ourselves and our investment response. Nevertheless, a real and deep-rooted engagement with this issue could realize a genuinely improved quality of life in all parts of the world, with dramatically better outcomes on human well-being, economic growth, and health. That opportunity is there today, and the report calls us to grasp it.