Wednesday, January 30, 2019

Climate Fish Tales

from the column What’s Natural? published in the Pacifica Tribune and 5 other SF Bay Area papers January 30, 2019

American folk lore is filled with stories of how Native Americans observed changes in wildlife and foretold future weather changes. I was fascinated by an 1800s story of Native Americans inhabiting regions around Marysville, California who had moved down into the river valleys during drought years. They then moved to higher ground before devastating floods occurred. Did they understand California’s natural climate cycles? Could changes in salmon migrations alert them? 

Observing salmon has certainly improved modern climate science. In the 1990s climate scientists struggled to understand why surface temperatures in the northwest sector of the Pacific Ocean had suddenly become cooler while temperatures in the eastern tropical Pacific suddenly warmed.  Climate models predicted no such thing. However, fishery biologists noted salmon abundance in Alaska underwent boom and bust cycles lasting 20 to 40 years. When Alaskan salmon populations boomed, their populations from California to Washington busted. Conversely, decades later when Alaskan populations busted, those more southerly populations boomed.

Scientists soon realized the observed alternating patterns in fish abundance not only coincided with those puzzling changes in ocean surface temperatures, but also with regional drought-flood cycles, glacier growth and retreat, and tree-line advances and retreats. Tree rings and lake sediments also recorded cycles of 5 major Sierra Nevada droughts alternating with wetter decades during the past 300 years. This all convinced scientists of the existence of a natural “ocean oscillation” driving climate change. This climate see-saw was finally named the Pacific Decadal Oscillation (PDO) in 1997. (Science uses the term “oscillation” to describe repeating cycles with general, but imprecise time periods.)

The newly characterized PDO had yet to be included in climate models. But progress in climate researchrecently argues the PDO largely explains western North America’s last 100 years of climate change. So how do we separate naturally caused weather extremes from human contributions? Unfortunately, few Americans are aware of these “cycles”. But if we don’t educate our children about natural climate change, the next generation will surely fall victim to every Chicken Little climate story told by scientifically illiterate politicians or by journalists who profit from sensationalism; if it bleeds, it leads!

Similar fish tales have been reported globally. In the Atlantic, a similar oscillation was officially recognized in 2000. But according to fishery records, that oscillation has been noted since the 15thcentury. Norwegian fisheries documented 30 to 60-year boom and bust cycles for herring, sardines and anchovies. In the 1930s Greenland experienced a warming rivaling today’s temperatures. Simultaneously Danish Arctic ice records showed extensive sea ice melt. This all coincided with intrusions of warm Atlantic waters that brought Atlantic cod and herring northwards. Fish retreated decades later coinciding with cooling temperatures and recovering sea ice. Today’s Arctic warming and reduced sea ice has likewise coincided with greater intrusions of warm Atlantic water. Will there be a return cycle of retreating Atlantic waters that causes sea ice to rebound again?

Finally, contrary to recent claims of “unprecedented” rapid warming, Greenland’s air temperatures warmed more rapidly during the 1920s to 30s causing melting around Greenland’s ice cap. After warm waters retreated, Greenland gained ice from the 1960s to the 90s. A new period of rapid melting began in the 90s but peaked in 2012. Since then, Greenland’s melting gradually subsided and Greenland gained ice in 2017 and 2018, perhaps signaling a new cooling phase. 

And there is a truly optimistic fish tale. Monterrey Bay Aquarium Research Institute’s senior scientist Dr. Francisco Chavez is a Peruvian oceanographer who studies the PDO and upwelling effects on marine life. The upwelling region off the coast of Peru is known as the most productive fishery in the world because robust upwelling brings nutrients from dark ocean depths up to the sunlit layers increasing photosynthesis. During the cold Little Ice Age - 1300 to 1850 AD - marine life off Peru’s coast was at a low point. Starting in the late 1800s as temperatures warmed, plankton rapidly increased, which promoted rapid increases in fish abundance. This dramatic improvement in marine life is well documented in preserved sediments.

To promote plant growth, commercial greenhouses add an additional 1000 ppm to the current 400 ppm of atmospheric COconcentrations. So, did marine life also increase due to rising levels of CO2? Or perhaps, because land temperatures warm faster than ocean temperatures, did stronger winds increase ocean upwelling? Whatever the drivers of the observed increases in ocean life, it appears likely that rising COcontributed definitive benefits. 

If we are to truly understand climate change and discern human contributions, these fish tales all suggest we must first account for natural oscillations that have surely been operating for millennia. So, to rephrase Mark Twain, ‘reports of the earth’s imminent death within 18 years, via rising CO2, are likely greatly exaggerated’.

Jim Steele authored Landscapes and Cycles: An Environmentalist’s Journey to Climate Skepticism

Wednesday, January 16, 2019

Disentangling California Droughts

Devastating droughts are a great concern. Droughts disrupt ecosystems, agriculture, and drinking water supplies. Contrary to headlines suggesting we have only 12 years before descending into climate hell with more severe droughts, historically, Californians are not experiencing more severe droughts. Despite low stream flows and withering plants, there’s no agreement on how to best define drought. Different methods suggest different severities for the same drought. Thus, the Intergovernmental Panel on Climate Change’s recent assessment, downgraded their ability to detect the causes of drought to “low confidence”.

Ocean circulation determines how much rain reaches the land. Each summer, California naturally experiences months of drought because storms carrying ocean moisture are blocked. Every few years, a rainy El Niño year alternates with drought producing La Niñas. But 20 years of more frequent La Niñas can cause 20 years of drought. To address natural precipitation shifts, California constructed ~1400 dams, storing water during wet years that can be released during drought years. Yosemite’s Hetch Hetchy reservoir supplies about 25% of San Francisco’s drinking water and 17% of its electricity. Misguided attempts to remove its dam would be disastrous for humans with scant environmental benefits.

NOAA scientists analyzed California’s 2011-2014 drought concluding it was dominated by a La Niña and natural variability. In contrast, their models suggested any greenhouse contribution was “very small”. Similarly, drought-sensitive tree rings suggested the extremely low precipitation was not unprecedented nor “outside the range of natural variability”. For 1200 years, extremely low rainfall happens a few times every century. 

However, because higher temperatures can theoretically increase evaporation and dry the land, some researchers define drought by calculating the Palmer Drought Severity Index (PDSI). Despite using the same tree rings, the PDSI transformed a natural California drought into the worst in 1200 years, evoking global warming fears. 

What to trust? 

Most scientists agree the PDSI is biased towards worse droughts, because it assumes higher temperatures always dry the land. However, the opposite is also true! Without moisture to absorb heat, drier conditions produce higher temperatures.  Studies using more accurate measurements than the PDSI find no increase in global droughts. 

Before significant COwarming was possible, Dust Bowl years from 1928-1939 and the 1950s drought were the most severe 20thcentury American droughts. La Niña-like ocean temperatures blocked rain storms and triggered the Dust Bowl while plowing up native grasses made it worse. More concerning is 2 century-long megadroughts between 900 AD and 1400 AD. Trying to survive increasing dryness Native Americans created dams and irrigation canals. But those droughts finally led to the demise of once thriving Pueblo Cultures such as Mesa Verde.  

Will our modern water infrastructure protect us if drought history repeats? 

Reducing our carbon foot print or whacky plans to shade the earth from the sun to lower global temperatures will have no effect. Lower temperatures may in fact increase major droughts. Droughts during the 1750s, 1820s, and 1850s-1860s were similar to the 1950s. During the cool 1500s, the southwestern United States and Mexico suffered decades long droughts of “epic proportions”.

Coincident with the Pueblo Culture’s demise, drought is detected in sediments of San Francisco Bay. Droughts reduce stream flows that normally flush the bay, allowing salty ocean water to encroach deeper into the Bay’s delta. Past droughts caused the Bay’s Suisun Marsh to become 40% saltier. Suisun Marsh is now considered the only sustainable habitat for a critically endangered fish, the Delta Smelt. The current theory for the Delta Smelt’s demise is agricultural diversions of freshwater raised salinity to intolerable levels. That perceived competition for freshwater has pitted farmers against efforts to save the smelt.  Learning how the smelt survived a thousand years of much higher salinity might provide a win-win solution. 

Agricultural and urban needs also compete with salmon survival. One promising win-win solution is having juvenile salmon develop in irrigated rice fields after hatching. Experiments show young salmon grow much bigger in rice fields. Additionally, low stream flows hamper salmon migration. But when enough water is naturally stored as groundwater, seasonal groundwater release can maintain adequate summer stream flows.  Unfortunately, landscape changes have caused stream channels to cut downwards, draining local groundwater and drying the land. Restoring streams and groundwater would provide great benefits.

During my research in the Sierra Nevada, a meadow we were monitoring began to dry; willows died, and bird populations crashed. Many suggested it was just what global warming models predict. However, we determined a railroad track built over 100 years ago had caused the meadow’s stream channel to cut downwards, draining its groundwater. I initiated a watershed restoration. Vegetation quickly recovered, and wildlife increased. Despite California’s years of extreme drought, the restored meadow remained wetter than it had before restoration and before the drought. 

So, I warn: knee-jerk reactions simply blaming climate change for devastating dryness, blind us to real causes and real environmental solutions.

Thursday, January 3, 2019

A Look at the Camp Wildfire in Paradise

In early December I surveyed the horrific Camp Fire disaster in Paradise. Having been director for 25 years of a university field station located in the heart of the Tahoe National Forest, I’ve been a “student” of fire ecology for 30 years and wanted a closer look at why row after row of homes completely incinerated while surrounding trees were merely scorched, with leaves and needles browned but not burnt? 

Torched Homes in Camp Fire with Spared Trees

Large fires have recently ravaged about 1.8 million California acres a year, prompting media and politicians to proclaim a “new normal” that’s “evidence of global warming”.  But UC Berkeley fire ecologists have calculated that before 1800, fires burned 4 million California acres each year (despite cooler temperatures). So what natural fire dynamics promote such extensive burning?

Wildfires have indeed increased since 1970, but that’s relative to previous decades of intensive fire prevention. As fire was recognized as a natural and necessary phenomenon for healthy ecosystems a new era began. In the 70s the US Forest Service moved away from extinguishing all fires by 10 AM the day after detection, switching to a “let it burn policy” if human structures were not endangered.

Paradise, unfortunately, sprung up amidst a forest dominated by Ponderosa pines. Largely due to frequent lightning strikes and dry summers, Ponderosa habitat endures fires about every 11 years. Fortunately for California’s coastal residents, lightning is rare. However, both regions are vulnerable to human ignitions, which start 85-95% of all fires. Recognizing this growing problem, a bipartisan bill was presented to Governor Brown two years ago to secure our power grid. Shockingly he vetoed it. That was a bad choice given the Camp Fire, Wine Country Fires and many more were sparked by an ageing electrical infrastructure. Recent studies show larger fires result from a confluence of human ignitions and high winds. But it is not just random coincidence. The high winds that spread these massive fires also blow down power lines that ignite those fires.

In 2008 the world’s foremost expert on fire history, Stephen Pyne lamented, “global warming has furnished political cover to encourage certain fire management decisions while allowing climate to take the blame.” How true. Both PGE and Governor Brown have blamed wildfires on climate change. 

When you build a camp fire, you intuitively understand fire ecology basics. You do not hold a match to a log no matter how dry. You start a camp fire with kindling. Fire ecologists call forest kindling, like dead grass, leaves and small shrubs, “fine fuels”. In dry weather “fine fuels” become highly combustible in a matter of hours, or at most days, even during the winter. Furthermore, California’s summer climate is naturally dry for 3-4 months, creating highly combustible habitat each and every summer.

Additionally, camp fires only smolder without enough air, so we huff and puff to get a burst of flames. Likewise, high winds turn a spark into a major conflagration. It was strong winds that rapidly spread the Camp Fire. The fast-moving flames, feeding on “fine fuels” littering the forest floor, generated enough heat to ignite flammable homes that then burned from the inside out; but only enough heat to char the bark of most surrounding trees.

Miraculously spared buildings dotting a devastated landscape made the case for creating “defensible spaces” by managing the “fine fuels”. Surveying one unscathed church, the fire clearly came within 100 feet, scorching the base of every encircling tree. But due to a parking lot and a well-manicured lawn, the lack of “fine fuels” stopped the fire in its tracks. Trees on the lawn were not even charred. The public would benefit greatly if wildfire news stories emphasized the need to create adequate defensible spaces. 

With high deserts to the east and the ocean to the west, California’s winds shift with the seasons. Land temperatures always change faster than the ocean’s. In the summer, warmer land surfaces draw in moist sea breezes. The resulting fog moistens coastal landscapes and reduces fire danger there. Thus, any warming, whether natural or CO2driven, should increase the fog.

In the autumn, the land cools faster than the ocean causing the winds to reverse direction. The colder it gets, the stronger the winds blow from the high deserts towards the coast, peaking in December. These winds are called Santa Annas in southern California. The Wine Country fires were spread by the Diablo winds. But regardless of the name, the science is the same.  Accordingly, it was November winds that fanned a spark into an inferno aimed directly at the heart of Paradise. 

It has long been known that due to these autumn and winter winds, much of California endures a dangerous fire season year-round.  On the optimistic side, any warming of the land during the cool seasons, whether natural or COdriven, should reduce these winds. Indeed, the natural drivers of wildfire are very complex, and maintaining a defensible space is our safest bet.