Why A Warming Climate Is Making This Spring So Cold (… and Last Spring So Warm)

Melting sea ice might not seem important to those of us living in the middle of a continent.  It is.

Weather and climate have always been complicated and difficult to understand, so it’s no wonder that climate change is a topic that confuses most of us.  The fact that most climate change discourse is more political than scientific these days makes things worse.  It’s hard to have reasonable discussions because most people’s opinions tend to be linked to whichever loud voices they listen to, and few of us understand climate science well enough to draw our own independent conclusions.

The poor groundhog has been a popular scapegoat for this year's cold spring temperatures.  In reality, both this year's cold spring and last year's warm spring are much more strongly tied to global warming and melting arctic ice.

The poor groundhog has been a popular scapegoat for this year’s cold spring temperatures. In reality, both this year’s cold spring and last year’s warm spring are much more strongly tied to global warming and melting arctic ice.

I’m certainly not going to wade into the politics of climate change, and I’m not qualified to get very far into climate science.  However, I did read something recently that clarified some things for me, so I’m hoping it will help you as well.  Thanks to Joel Jorgensen for passing along the article that spawned this post.

One of the most difficult things to understand about global warming is that it can make local temperatures get colder as well as warmer.  Here in Nebraska, we’re experiencing a very cold spring – if you can call it spring – this year, but had a very warm spring in 2012.  How, you might ask, is it possible that both the warm spring of 2012 and the cold spring of 2013 are a result of global warming?

Last year at this time, pussytoes was starting to bloom in our Platte River Prairies.  This year, there's no indication that they're anywhere close to that stage.

Last year at this time, pussytoes was starting to bloom in our Platte River Prairies. This year, there’s no indication that they’re anywhere close to that stage.

Scientists have long suggested that more extreme weather patterns (including warm and cold, wet and dry) are a consequence of global warming, but I’ve never had more than a vague understanding of why.  Apparently climate scientists are still figuring it out too, but new research published by Jennifer Francis and Stephen Vavrus in Geophysical Research Letters seems to help.  After reading a summary of the work in the Omaha World Herald and stumbling through the actual scientific journal article, here is my best shot at explaining the results.

First two pieces of background information you need to understand.  This is based on my own rudimentary understanding of this topic, so please take it as such.

1.  The warming of the Arctic and the subsequent loss of sea ice is reducing the contrast in temperature between the cold Arctic region and the warmer center of the globe.

2. The contrast between warm and cold areas of the globe is a major driver of weather patterns because it creates an imbalance in atmospheric pressure.  The jet stream is the major current of air that tends to run along the boundary between those cold and warm areas (there is actually more than one jet stream, but let’s not get into that). When the jet stream is strong, it moves strongly in a relatively straight west to east direction.  However, when it is weak, it makes large north-south loops as it ambles slowly to the east.

Ok, armed with that background knowledge, here’s what’s happening with global warming.  Arctic air to the north of us is less cold than it used to be, so there is less contrast between that air and the warm air to our south.  That weakens the jet stream, causing it to make large loops as it moves from west to east.  Equally importantly, those loops tend to stay in the same place for a long time.

When Nebraska is inside a southward loop of the jet stream, the jet stream’s current allows lots of cold arctic air to come down from the north.  That’s what is making our 2013 spring so cold.  The opposite is true when we’re inside a northward loop – our weather is dominated by warm air coming up from the south, creating a weather pattern such as the one we saw in 2012.  Because a weak jet stream causes those loops to not only be greater in size, but also to stick around longer weather patterns persist for longer periods than they otherwise would.  If the weather extra warm for a long time, we tend to have drought, but extended weather periods can just as easily lead to flooding, extended cold temperatures, etc. – depending upon whether we’re north or south of the jet stream current.

When we are inside a southward loop of the jet stream (top picture) cold air from the north dominates our weather.  When we are inside a northward loop of the jet stream, warm air moves in from the south.

When we are inside a southward loop of the jet stream (top picture) cold air from the north dominates our weather. When we are inside a northward loop of the jet stream (bottom picture) warm air moves in from the south.

Of course, there is much more to weather and climate than just jet stream loops, so a slower, more wandering jet stream is only part of the story.  In addition, understanding why we’re getting more extreme and extended weather patterns doesn’t change the situation – it just explains it.  I’ve written in the past about some climate change adaptation strategies for those interested in prairie management, restoration, and conservation.  A big part of our responsibility is to make prairies as ecologically resilient as possible.  

Since creating and sustaining resilience in prairies is largely dependent upon factors we’ve been working on for a long time anyway – species diversity, habitat size and redundancy, etc. – not much changes when we add climate change into the mix, except perhaps that we should feel a little more urgency.

Again, I’m no climate scientist, so I’m trying to explain things I barely understand myself.  Please correct me if I’ve mis-stated something or explained things poorly.

The Right Metaphor for Prairie Restoration

Prairie restoration can be a powerful tool for grassland conservation, but we’re not taking advantage of its full potential.  Too often, we think and talk about prairie restoration (aka prairie reconstruction) in the wrong way.  Instead of trying to restore an ecosystem, we try to reproduce history.

Nelson Winkel, land manager for The Nature Conservancy’s Platte River Prairies, harvests grass seed using a pull-behind seed stripper.

I was in Washington D.C. a couple weeks ago and visited Ford’s theater, where President Lincoln was assassinated in 1865.  After the death of the president, the building went through drastic changes, including being completely gutted after a partial collapse of the interior.  By the time the decision was made to restore the building for use as a historic site, the National Park Service basically had to start from scratch.  Regardless, through painstaking research and a lot of hard work, the theater was rebuilt to closely resemble Ford’s theater of 1865.

The rebuilding of Ford’s theater is a decent metaphor for much of the early prairie restoration (or reconstruction) work dating back to the 1930’s in North America – as well for some of the restoration work that continues today.   In the case of prairie restoration, someone identifies a tract of land that used to be prairie but has been converted into something completely different (usually cropland), and tries their best to restore what was there before it was converted.  Just as in the restoration of Ford’s theater, the prairie restoration process requires lot of research and hard work to identify, find, and reassemble what had been there before.

Unfortunately, the Ford’s theater approach has turned out to be a poor fit for prairie restoration.  Prairies aren’t buildings that have specific architectural plans and well-defined pieces that can be collected and assembled to create a pre-defined end product.  Prairies are dynamic ecosystems that are constantly changing and evolving, and their components include organisms that interact with each other in complex ways.  Trying to recreate a prairie that looks and functions just as it used to – especially on a small isolated tract of land – is nearly impossible.

Reseeded prairie at The Nature Conservancy’s Kankakee Sands Restoration Project in Indiana. If the plant community today looks different than it did before it was farmed, is that really a failure of the restoration project?

That doesn’t mean small scale prairie restoration is a bad idea.  I think reestablishing vegetation that is similar to what was at a site many years ago can have tremendous historic and educational value, and can also provide important habitat for many grassland species.  Where this kind of prairie restoration falls flat is when we expect too much from it.  It’s really easy to find glaring differences between the restored prairie and what we know or think used to be there – soil characteristics are different, insect and wildlife species are missing, plant species are too common or too rare, etc.  These “failures” have led some people in conservation and academia to become disillusioned with the whole concept of prairie restoration.

In reality, prairie restoration has proven to be very successful, and is a tremendous tool for grassland conservation.  We just need to find and apply a better metaphor.

A Better Metaphor for Ecological Restoration

Unlike efforts to restore old buildings, prairie restoration projects should not be aimed at recreating something exactly as it existed long ago.  Instead, effective prairie restoration should be like rebuilding a city after large portions of it are destroyed in a major disaster.  When reconstructing a metropolitan area, replicating individual structures is much less important than restoring the processes the inhabitants of the city rely on.  The people living and working in a city depend upon the restoration of power, transportation, communication, and other similar functions.  Those people don’t care whether roads, power lines, or communication towers are put back exactly as they were before – they just want to be able to get the supplies and information they need, and to travel around so they can to do their jobs and survive.  Restoration success is not measured by how much the rebuilt areas resemble the preexisting areas, but by whether or not the city and its citizens can survive and thrive again.

Similarly, restoration of fragmented prairie landscapes should not be an attempt to recreate history.  It should be an attempt to rebuild the viability of the species – and, more importantly, the processes – that make the prairie ecosystem function and thrive.  Success shouldn’t be measured at the scale of individual restoration projects, but at the scale of the resultant complex of remnant and restored prairies.  Are habitat patches sufficiently large that area-sensitive birds can nest successfully?  Are insects and animals able to travel through that prairie complex to forage, mate, and disperse?  Are ecological processes like seed dispersal and pollination occurring between the various patches of habitat?  When a species’ population is wiped out in one part of the prairie because of a fire, disease, or other factor, is it able to recolonize from nearby areas?

Pollination is an example of an important process that drives prairie function. Increasing the size and/or connectivity of prairies by restoring areas around and between prairie fragments can enhance the viability of pollination and other processes.

At first glance, choosing the appropriate metaphor for prairie restoration may seem insignificant compared to other challenges we face in grassland conservation.  However, if we’re going to successfully restore the viability of fragmented prairies, we can’t afford to waste time and effort worrying about whether or not we’ve matched pre-European settlement condition, or any other historical benchmark.  Instead, we need to focus on patching the essential systems back together.

After all, we’re not building for the past, we’re building for the future.

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Read more on this subject…

– An earlier blog post about using prairie restoration as a landscape scale conservation tool.

– A prairie restoration project case study, with ideas about how to measure its success.

– Some recent early attempts we’ve made to measure restoration success by looking at the responses of bees and ants.

– A post about the importance and definition of ecological resilience in prairies.