By: LOUIS SPANIAS, Sustainability Program Manager
Earlier this month, the Intergovernmental Panel on Climate Change (IPCC) released a Special Report (SR15), “Global Warming of 1.5°C,” which quickly grabbed headlines and found its way into our newsfeeds and newspapers. These headlines and accompanying op-eds painted a pretty dire picture. Just to reel off a few:
- “We have 12 years to limit climate change catastrophe, warns UN” – The Guardian
- “UN report predicts catastrophic consequences if greenhouse gas emissions not reduced by 2030” – The Hill
- “Planet has only until 2030 to stem catastrophic climate change, experts warn” – CNN
- “A major new climate report slams the door on wishful thinking” – Vox
- “Final call to halt ‘climate catastrophe’” – BBC News
- “U.N. report on global warming carries life-or-death warning” – Associated Press
The titles alone send a particular message: we have twelve years to figure out how to significantly decarbonize our economies or face catastrophic consequences. For most readers, the rhetoric paints a morbid picture – but is that what the IPCC is telling us in this report? To find out, let’s delve deeper into “Global Warming of 1.5°C.”
SR15 is a highly substantive and detailed report. Like the IPCC’s Assessment Reports (released every six years – most recently in 2014), this Special Report synthesizes cutting edge climate science into a series of prognoses and illustrations towards providing a reasonable assessment of what the world will look like having warmed 1.5°C above pre-industrial levels. For context, the IPCC and climate science community at large have consistently warned over the years that global warming should not exceed 1.5°C if we want to avert the worst effects of climate change – which as this report emphasizes is not an arbitrary threshold. The Paris Agreement, which entered into force in late 2016, aims to keep global warming well below 2°C but encourages signatories to pursue efforts that would limit warming to 1.5°C. When the Paris Agreement was adopted, the IPCC was invited to prepare this special report, which will be followed by a few more special reports in the lead-up to the AR6. In short, this document is a clear and explicit encapsulation of how life on Earth will likely look should we not meet the 1.5 °C threshold based on current climate science – as well as a preeminent guideline of what needs to happen now to prevent it.
It is also important to note that much of the statements made in the report are accompanied by varying degrees of confidence in the underlying scientific evidence: very low, low, medium, high, and very high. They also provide likelihoods of certain climate change outcomes: virtually certain (99-100% probability), very likely (90-100%), likely (66-100%), about as likely as not (33-66%), unlikely (0-33%), very unlikely (0-10%), and exceptionally unlikely (0-1%). This is consistent with the language of AR5, while highlighting areas where science has progressed, and uncertainty declined. It’s also important to note that the citations in this blog come from the “Summary for Policymakers,” which accompanies but also consolidates the chapters and supplementary materials that comprise SR15.
What the Report Says
The seminal statement of the report comes first. “Human activities are estimated to have caused approximately 1.0°C of global warming above pre-industrial levels, with a likely range of 0.8°C to 1.2°C. Global warming is likely to reach 1.5°C between 2030 and 2052 if it continues to increase at the current rate. (high confidence)”. In other words, since the beginning of the industrial period over 100 years ago, we’ve already warmed the earth about a whole degree Celsius – and we are bound to hit the 1.5-mark sometime in the next couple of decades. This warming “will persist for centuries to millennia and will continue to cause further long-term changes in the climate system.” However, the IPCC notes that getting to 1.5°C warming is unlikely to be the result of emissions up to the present, but instead the outcome of forthcoming emissions. Subsequently, the IPCC emphasizes the need for serious and immediate action, and states that maintaining the status quo puts the 1.5°C threshold just around the corner.
The IPCC then highlights the impacts of warming on natural and human systems, many of which “have already been observed.” Various ecosystems and their accompanying services have already changed as a result, and should we exceed the 1.5°C warming threshold, these impacts (including ecosystem loss) might be irreversible. The ongoing warming of the climate system will also entail increases in “mean temperature in most land and ocean regions (high confidence), hot extremes in most inhabited regions (high confidence), heavy precipitation in several regions (medium confidence), and the probability of drought and precipitation deficits in some regions (medium confidence).” This bit might hit closer to home for some readers, who may have already observed warmer temperatures in recent years in their neck of the woods, but summarily the increased warming in the climate system will create shifts in regional temperatures and longer-term climate events (e.g. droughts) depending on where you are in the world. Anticipated outcomes regarding precipitation are stated with lower confidence typically because differing models of the climate system offer less consensus on a regional level regarding expected rainfall as the world warms, which is not necessarily the case with temperature. However, as the IPCC notes, the risks from drought or lacking precipitation only increase as the world warms.
Relatedly, the IPCC forecasts sea level rise well through 2100 even if we successfully limit warming to 1.5°C this century, though the rate and volume to which the sea level rises (and consequently our ability to adapt to it) will depend greatly on how the world handles its greenhouse gas emissions going forward. Models suggest a rise in global mean sea level between 0.26 to 0.77 m by 2100 in a 1.5°C scenario, and that range shifts up another 0.1 m in a 2°C scenario (with medium confidence). However, in larger time scales, the bigger concerns lie with melting ice in Antarctica and Greenland: “Marine ice sheet instability in Antarctica and/or irreversible loss of the Greenland ice sheet could result in multi-metre rise in sea level over hundreds to thousands of years… [which] could be triggered around 1.5°C to 2°C of global warming (medium confidence).” At any rate, rising sea levels present serious risks to people inhabiting small islands or low-lying coastal areas and deltas.
The report addresses additional impacts , including species loss and extinction, increases in ocean acidity and related declines in marine ecosystem health and biodiversity, the “disproportionately higher risk of adverse consequences” on vulnerable and/or coastal communities (including increased poverty and other related disadvantages), effects on human health and risk from disease, declining food availability in certain regions of the world, effects on global economic growth, and more. Consistently emphasized through each of these topics is the importance of warming leveling out at or not reaching 1.5°C, and the exacerbated consequences in each category as warming increases to 2°C and beyond.
It is from this point forward that the report turns to adaptation and emissions pathways, during which the IPCC first emphasizes the need for adaptive measures that could reduce the risks of climate change. However, some losses or damage on human and natural systems are already viewed as inevitable and show that there are limits on our ability to adapt or prepare for certain changes. As for emissions, the IPCC states the following: “In model pathways with no or limited overshoot of 1.5°C, global net anthropogenic CO2 emissions decline by about 45% from 2010 levels by 2030, reaching net zero around 2050.” This pathway “would require rapid and far-reaching transitions in energy systems, land, forest and agricultural management, urban and infrastructure (including transport and buildings), and industrial activities (high confidence),” and the IPCC consequently lays out several opportunities that countries could pursue towards that end. Even so, the IPCC emphasizes that such transitions “are unprecedented in terms of scale, but not necessarily in terms of speed,” meaning that this work could be done quickly, but perhaps not to the magnitude required. In any case, capping warming at that threshold requires removing carbon dioxide from the atmosphere – whether it be through afforestation and reforestation, carbon capture and storage, or other methods.
Up to this point, the IPCC has made it clear that a world that has warmed 1.5°C from pre-industrial levels poses serious threats to ways of life as we know them and expresses in great detail where action is needed. However, where the picture gets really bleak comes after: “Estimates of the global emissions outcome of currently nationally stated mitigation ambitions as submitted under the Paris Agreement would lead to global greenhouse gas emissions in 2030 of 52-58 GtCO2eq yr. Pathways reflecting these ambitions would not limit global warming to 1.5°C, even if supplemented by very challenging increases in the scale and ambition of emissions reductions after 2030 (high confidence). Avoiding overshoot and reliance on future large-scale deployment of carbon dioxide removal can only be achieved if global CO2 emissions start to decline well before 2030 (high confidence).” In other words, the stated commitments of signatories to the Paris Agreement will not be enough to stay below the threshold, though frankly, the climate science community had already pointed out this was the case.
The report concludes with a series of broader statements regarding the measures needed to stay in bounds, pointing to a greater international and collective focus on the United Nations Sustainable Development Goals (SDGs), as well as adaptive/mitigative decisions and policy choices across government, finance, technology, environmental management, and socio-cultural systems. Some of the solutions proposed in the report are certainly viable, but some require behavioral change while others need to come from advances in technology that remain in testing or development. However, at its core, the latter segment SR15 is a call for comprehensive and collaborative decision-making and more immediate and aggressive action on global warming.
Thus, there is quite a bit to take away from SR15, and a closer look at the report makes it clear that there is truth to the headlines. Granted, the IPCC avoids the use of normative or opinionated terminology, so you won’t find the words “catastrophe” or “catastrophic” in SR15, but the report points to 2030 as the deadline if we hope to cap global warming at 1.5°C this century – and the consequences on human life, natural ecosystems, and wildlife could indeed be catastrophic if we do not act. Current national commitments under the Paris Agreement are certainly not enough – with or without the United States (which is the world’s 2nd largest emitter of greenhouse gases).
Related to this point, the IPCC reminds us that climate change is not 12 years away. For as pointed as the language of the report is around the year 2030, climate change has been and is already happening. The report clearly states that the impacts of anthropogenic greenhouse gas emissions up to the present will be felt well through the end of this century – whether we successfully cap GHG emissions or not.
Another serious point for consideration is the assertion by multiple prominent climate scientists that even the IPCC’s prognoses are a milder depiction of the problem. Michael E. Mann, a renowned climate scientist at Pennsylvania State University, tweeted soon after the report was released: “To those who say that the #IPCC is alarmist: if anything, it is the opposite. Once again, with their latest report, they have been overly conservative (i.e., erring on the side of understating/underestimating the problem).” In another tweet, Mann emphasizes that the report “overestimates [the] remaining “carbon budget” for avoiding 1.5°C and 2°C warming by ignoring problems [climate scientists] discussed in the literature.”
Finally, the largest takeaway is that the IPCC’s report is not purely a warning about what’s to come, but it is also a shot in the arm to governments and organizations around the world that for every ounce of effort given to curbing emissions, we must increasingly give attention to adaptation and resilience efforts. Nearly half of the provided “summary for policymakers” is oriented around adaptive measures that governments should take, especially where populations are most vulnerable to the impacts of climate change. In short, for as much as we must cut carbon emissions and sequester carbon, we must also be ready for what is already in the forecast.
The report will feel dark to many who read it, but it is as comprehensive an assessment of the situation at present as we have. The report is not only a reiteration of what the IPCC has been telling us for years but also an updated set of predictions and action points if we have hopes of meeting a 2°C threshold, let alone 1.5°C. The responsibility falls not only on government and industry but on all of us, especially when having the opportunity to vote and hold elected officials accountable for their stance on climate change.