you're reading...

Climate Change

The future according to the Paris Agreement? Not so simple.


Source: Seneviratne, S. I.; Rogelj, J.; Séférian, R.; Wartenburger, R.; Allen, M. R.; Cain, M.; Millar, R. J.; Ebi, K. L.; Ellis, N.; Hoegh-Guldberg, O.; Payne, A. J.; Schleussner, C.; Tschakert, P.; and Warren, R. F. The many possible climates from the Paris Agreement’s aim of 1.5 °C warming, Nature 558, 41-45. (2017)


The bottom line of the years in the making, 178-country Paris Agreement was simple: aim to limit anthropogenic warming to 1.5˚ C, and go no higher than 2 ˚C. While framing the goal in terms of a mean temperature increase is concise and appealing, it doesn’t say much about what the global climate might look like if we succeed. In their recent paper, Dr. Sonia Seneviratne of the Swiss Federal Institute of Technology in Zurich and her team of international collaborators bring together results from a variety of studies to clearly show that meeting the goal of the Paris Agreement could result in a wide range of possible future climate scenarios.

Seneviratne and the scientists note that the first source of uncertainty in the outcome of the Paris Agreement lies in the very definition of global temperature. To exclude the influence of natural climate variability, the average global temperature needs to be measured over a set time frame, which the World Meteorological Organization states should be at least 30 years. Moreover, there are open questions about where the world’s temperature will be taken to satisfy the “global” part of the expression. The entire earth’s surface is not continuously monitored, necessitating decisions about where to take temperature measurements and how to fill the gaps between these points. But even when comparing scenarios in which the mean temperatures are defined in the same way, several other factors make for a wide spread in possible outcomes of a 1.5 ˚C-warmed planet.

First: timing matters. Seneviratne and her team remind us that the speed of human action resulted in vastly different future climate scenarios. There are components of human-caused changes that have significant lags, for example sea-level rise, which is a response to past warming. If we hit a 1.5-˚C warmer world by 2050 versus 2200 (and are able to stabilize the mean global temperature in both cases), we’ll be experiencing the effect of sea level rise and other delayed changes much sooner. This more rapid global warming might cut short the period for adaptation afforded to organisms and ecosystems. The consequences for humans could be similar if communities are unable to brace for the local changes that come with rising global temperature.

While timing is important, Seneviratne and her colleagues show that there is even more spatial vaiability within the predictions of what a 1.5 ˚C warmer world might look like. Capping the mean global warming at 1.5 ˚C does not mean that everywhere on earth will stay under this limit. This is perhaps the most alarming part of the uncertainty in the predictions. It is possible that everywhere on earth undergoes only a slight temperature change, but it is also possible that some places undergo extreme warming while other places cool (Figure 1, 2). One possibility included in the array of predictions is that nighttime temperatures in the Arctic increase by 7 ˚C or more, while the global average of +1.5˚C is still maintained. The geographic differences in warming depend on a number of factors. These factors include how much the sun can heat different regions, how heat interacts with different landscape (by melting snow or drying soil), and also the natural local climate variability (e.g. El Niño events or seasonal monsoons). The fact that any number of spatial variations in warming can still satisfy the 1.5 ˚C goal goes to show that a huge variety of future outcomes are possible under this goal, with varying degrees of detriment to regions around the world.


Figure 1. Illustration of the divergence in outcomes despite both results satisfying the 1.5 ˚C warming target. On the left is the current climate, with one region having a mean temperature of 28 ˚C (82.4 ˚F), and another with a mean of 0 ˚C (32 ˚F). At the top right is a future scenario in which both regions warm only 1.5˚C (2.7 ˚F), and below it an also possible scenario of one region warming by 17.1 ˚F to 99.5 ˚F with another area on the globe cooling by the same amount. Reprinted by permission from Springer Nature: Nature Perspectives, The many possible climates from the Paris Agreement’s aim of 1.5 °C warming, Sonia I. Seneviratne et al., 2018.


Figure 2. 25th and 75th (left and right columns, respectively) percentile of possible outcomes for a 1.5 ˚C warming scenario, referring to the being near the lower and upper range of possible temperature changes. The top row is overall mean temperatures, the middle row maximum daily temperatures, and the bottom row minimum nighttime temperatures. Reprinted by permission from Springer Nature: Nature Perspectives, The many possible climates from the Paris Agreement’s aim of 1.5 °C warming, Sonia I. Seneviratne et al., 2018.


The consensus in the scientific literature is that to limit global warming, we must reach the point of releasing zero carbon emissions, and that what the future will look like depends on when we are able to reach this point. Included in the Paris Agreement is the aim of reaching zero emissions by the end of the 21st century. But according to some studies, we would need to be there by 2020 at the latest in order to maximize the goal of limiting warming to 1.5 ˚C.

The crux of Seneviratne et al.’s paper is that capping warming at 1.5 ˚C isn’t a panacea, nor is it a simple task. Regardless of whether the Paris Agreement goals are met, there remain risks for dangerous and destructive future climates. In order to ensure a safe and livable planet for future generations, we must take seriously the threat of climate change and act immediately to reduce carbon emissions.


No comments yet.

Post a Comment


  • by oceanbites 3 months ago
    Happy Earth Day! Take some time today to do something for the planet and appreciate the ocean, which covers 71% of the Earth’s surface.  #EarthDay   #OceanAppreciation   #Oceanbites   #CoastalVibes   #CoastalRI 
  • by oceanbites 4 months ago
    Not all outdoor science is fieldwork. Some of the best days in the lab can be setting up experiments, especially when you get to do it outdoors. It’s an exciting mix of problem solving, precision, preparation, and teamwork. Here is
  • by oceanbites 5 months ago
    Being on a research cruise is a unique experience with the open water, 12-hour working shifts, and close quarters, but there are some familiar practices too. Here Diana is filtering seawater to gather chlorophyll for analysis, the same process on
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on  #oceanbites  we are featuring Hannah Collins  @hannahh_irene  Hannah works with marine suspension feeding bivalves and microplastics, investigating whether ingesting microplastics causes changes to the gut microbial community or gut tissues. She hopes to keep working
  • by oceanbites 6 months ago
    Leveling up - did you know that crabs have a larval phase? These are both porcelain crabs, but the one on the right is the earlier stage. It’s massive spine makes it both difficult to eat and quite conspicuous in
  • by oceanbites 6 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring Cierra Braga. Cierra works ultraviolet c (UVC) to discover how this light can be used to combat biofouling, or the growth of living things, on the hulls of ships. Here, you
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Elena Gadoutsis  @haysailor  These photos feature her “favorite marine research so far: From surveying tropical coral reefs, photographing dolphins and whales, and growing my own algae to expose it to different
  • by oceanbites 7 months ago
    This week for  #WriterWednesday  on Oceanbites we are featuring Eliza Oldach. According to Ellie, “I study coastal communities, and try to understand the policies and decisions and interactions and adaptations that communities use to navigate an ever-changing world. Most of
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Jiwoon Park with a little photographic help from Ryan Tabata at the University of Hawaii. When asked about her research, Jiwoon wrote “Just like we need vitamins and minerals to stay
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  on  #Oceanbites  we are featuring  @riley_henning  According to Riley, ”I am interested in studying small things that make a big impact in the ocean. Right now for my master's research at the University of San Diego,
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Gabby Stedman. Gabby is interested in interested in understanding how many species of small-bodied animals there are in the deep-sea and where they live so we can better protect them from
  • by oceanbites 8 months ago
    This week for  #WriterWednesday  at  #Oceanbites  we are featuring Shawn Wang! Shawn is “an oceanographer that studies ocean conditions of the past. I use everything from microfossils to complex computer models to understand how climate has changed in the past
  • by oceanbites 9 months ago
    Today we are highlighting some of our awesome new authors for  #WriterWednesday  Today we have Daniel Speer! He says, “I am driven to investigate the interface of biology, chemistry, and physics, asking questions about how organisms or biological systems respond
  • by oceanbites 9 months ago
    Here at Oceanbites we love long-term datasets. So much happens in the ocean that sometimes it can be hard to tell if a trend is a part of a natural cycle or actually an anomaly, but as we gather more
  • by oceanbites 10 months ago
    Have you ever seen a lobster molt? Because lobsters have exoskeletons, every time they grow they have to climb out of their old shell, leaving them soft and vulnerable for a few days until their new shell hardens. Young, small
  • by oceanbites 10 months ago
    A lot of zooplankton are translucent, making it much easier to hide from predators. This juvenile mantis shrimp was almost impossible to spot floating in the water, but under a dissecting scope it’s features really come into view. See the
  • by oceanbites 11 months ago
    This is a clump of Dead Man’s Fingers, scientific name Codium fragile. It’s native to the Pacific Ocean and is invasive where I found it on the east coast of the US. It’s a bit velvety, and the coolest thing
  • by oceanbites 11 months ago
    You’ve probably heard of jellyfish, but have you heard of salps? These gelatinous sea creatures band together to form long chains, but they can also fall apart and will wash up onshore like tiny gemstones that squish. Have you seen
  • by oceanbites 12 months ago
    Check out what’s happening on a cool summer research cruise! On the  #neslter  summer transect cruise, we deployed a tow sled called the In Situ Icthyoplankton Imaging System. This can take pictures of gelatinous zooplankton (like jellyfish) that would be
  • by oceanbites 1 year ago
    Did you know horseshoe crabs have more than just two eyes? In these juveniles you can see another set in the middle of the shell. Check out our website to learn about some awesome horseshoe crab research.  #oceanbites   #plankton   #horseshoecrabs 
WP2Social Auto Publish Powered By : XYZScripts.com