//
you're reading...

Climate Change

Slightly Refreshing News In A Time of Drought

Article

Delworth, T.L., Zeng, F., Rosati, A., Vecchi, G.A., Wittenberg, A.T., (2015), A link between the hiatus in global warming and the North American drought, Journal of Climate 28, 3834-3845, doi: 10.1175/JCLI-D-14-00616.1

 

Background

Flip on the evening news and you will likely hear about the drought in western North America. Although the drought has been in place for a decade, we have hit a major turning point where the daily lives of people living in California have been disrupted through mandatory water restrictions. Tune in to certain radio or cable news stations, particularly those with strong political agendas and you may find yourself on the receiving end of a diatribe against climate scientists with arguments of global cooling (read: warming hiatus) over the past decade. The correlation between these two climate irregularities should stir up the scientist within us all. Could there be a causality of these two news-worthy topics? Are we to blame, or are these phenomena the result of natural variability?

The term warming hiatus refers to stagnation in global mean surface warming over the past decade. The cause of the warming hiatus has been explored and linked to increased speeds of the Pacific’s easterly trade winds and cooling of the surface of the eastern Pacific ocean over the last decade. For more on how increased winds and reduced surface temperatures in the Pacific Ocean and the connection with the warming hiatus, have a look at the coverage of England et al., 2014 . Scientists have also made connections between increased easterly trade winds in the Pacific to other ocean basins. Check out McGregor et al., 2014 to dive in deeper!

 

Methodology

This study aims to add to the body of knowledge of the relationships between the increase in Pacific easterly trade winds and global climate using climate modeling experiments. The purpose of climate models is to best represent the physics of Earth’s atmosphere and oceans to answer questions about what the future climate will bring. For example, scientists seeking to understand how increased wind speeds impact sea surface temperature can use climate models to explore this relationship. Using these models, scientists can simulate future increases in equatorial winds, and observe how sea surface temperature responds in the coming decades. Scientists consider models to be informative if the models are able to predict climate conditions over a period of time in which accurate observational data is available for comparison. For example, a good model using accurate greenhouse gas concentrations will spit out global temperature trends over the 20th century that are consistent with observations from weather stations over the same time interval. Of course, this example is very simplistic to demonstrate how climate models can be useful for making projections of climate into the future.

 

Figure 1. Sea surface temperature deviation from modeling simulations.   These images show the spatial changes in temperature from 2002 – 2012 resulting from  increased easterly trade winds.  Cool colors represent decreasing surface ocean temperatures, whereas warm colors represent increasing temperature.

Figure 1. Response of sea surface temperature from modeling simulations.
These images show the spatial changes in temperature from 2002 – 2012 resulting from increased easterly trade winds. Cool colors represent decreasing surface ocean temperatures, whereas warm colors represent increasing temperature.

Results

Redundancy in science can be a good thing: the results of this study largely agree with those of England et al., 2014. Delworth et al. report that the modeling simulations show the same hiatus in global surface temperatures over the past decade in response to the increase in Pacific easterly trade winds (Figure 1). They also acknowledge that there have been studies that have linked cool eastern Pacific sea surface temperatures with drier than normal conditions over western North America (Figure 2). The remaining question was whether the changes in precipitation were due to anthropogenic climate change (the increase in atmospheric concentrations of greenhouse gases) or to the changes in wind strength in the equatorial Pacific. By separately considering the drought response to changes in winds and the drought response as a result of increased greenhouse gases, the authors were able to attribute 92% of the reduced precipitation to changes in winds. This result strongly connects the North American drought to the warming hiatus and increased trade winds. For this reason, the North American drought cannot be considered a response to anthropogenic climate change, just as the warming hiatus is due to natural variability in the climate system.

Figure 2.  Comparison of changes in precipitation from observations and modeling simulations. Colors represent the daily precipitation in mm/day, and averaged over the course of a year.  Warm colors represent very low precipitation and drought-like conditions.  Observations of precipitation are shown in (a), whereas precipitation from modeling simulations are shown in (b,c,d).

Figure 2. Comparison of changes in precipitation from observations and modeling simulations.
Colors represent the daily precipitation in mm/day, and averaged over the course of a year. Warm colors represent very low precipitation and drought-like conditions. Observations of precipitation are shown in (a), whereas precipitation from modeling simulations are shown in (b,c,d).

 

Significance

So are humans off the hook for climate change? Are SUVs back “in” and hybrids destined for the junkyards? It is refreshing to consider that we are not responsible for the lack of precipitation, but by no means should this be a call for celebration. I’ll leave you with the latest IPCC assessment report if you are not convinced. One may ask: Well shouldn’t the drought come to an end as the warming hiatus wanes? The models predict that the warming hiatus will indeed come to the end, having only lasted between one or two decades, though ocean temperatures will remain persistently cool over the eastern Pacific (Figure 3). As a result, drought conditions are still expected to persist over western North America, but at a level that is not quite as severe. Put away those balloons and noise-makers!

Figure 3.  Future response of air and ocean temperature and precipitation. Despite the return of surface air warming (a), cool eastern equatorial Pacific surface temperatures persist (b) and drought-like conditions continue in western North America (c).

Figure 3. Future response of air and ocean temperature and precipitation.
Despite the return of surface air warming (a), cool eastern equatorial Pacific surface temperatures persist (b) and drought-like conditions continue in western North America (c).

 

How has the North American drought affected you? Is it reassuring that we aren’t the cause? Sound off in the comments below!

Discussion

No comments yet.

Post a Comment

Instagram

  • by oceanbites 4 days 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 2 weeks 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 3 weeks 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 1 month 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 2 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 2 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 2 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 2 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 2 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 3 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 4 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 4 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 4 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 5 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 6 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 6 months 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 
  • by oceanbites 7 months ago
    Feeling a bit flattened by the week? So are these summer flounder larvae. Fun fact: flounder larvae start out with their eyes set like normal fish, but as they grow one of their eyes migrates to meet the other and
  • by oceanbites 7 months ago
    Have you seen a remote working setup like this? This is a photo from one of our Oceanbites team members Anne Hartwell. “A view from inside the control can of an underwater robot we used to explore the deep parts
  • by oceanbites 8 months ago
    Today is the day of  #shutdownacademia  and  #shutdownstem  and many of us at the Oceanbites team are taking the day to plan solid actions for how we can make our organization and the institutions we work at a better place
  • by oceanbites 8 months ago
    Black lives matter. The recent murders of Ahmaud Arbery, Breonna Taylor, and George Floyd have once again brought to light the racism in our country. All of us at Oceanbites stand with our Black colleagues, friends, readers, and family. The
WP2Social Auto Publish Powered By : XYZScripts.com