Category Archives: Climate Change

Hot Weather Affects Maple Sugar Season

Maple sugar bucket hanging on a tree (photo from Wikimedia Commons)
Bucket collecting maple sap to make maple syrup (photo from Wikimedia Commons)

28 February 2024

The month of March is traditionally the best month for tapping maples to collect sap for maple syrup. The sap runs best with daytime temperatures above freezing and nights below freezing. When the days are too hot the sap becomes bitter. When the nights don’t freeze the sap stops running and the season is over.

This winter we’ve had yo-yo weather in the Northeast and Great Lakes states. You can see it in the forecast highs this week from Tuesday 27 Feb through Sat 2 March. The cold front coming through today will result in two nights below freezing. Then temperatures will rise again into the 60s. You can see the new blob of hot weather approaching from the Great Plains on Saturday 2 March.

Maple sugar farmers have had to adjust by starting the season whenever the sap runs — in Pennsylvania that might mean January — and pausing the season when the temperature goes up too high in hopes it will drop again.

This news article from Minnesota shows what their maple farmers are dealing with.

video embedded from KSPT5 Eyewitness News

Right Now You Can Kayak in Death Valley

Kayaking on Lake Manly in Death Valley (photo from Wikimedia Commons)

26 February 2024

In case you missed it …

During the Ice Age, the Pleistocene 2.58 million to 11,700 years ago, there was a lake 600 feet deep in Death Valley where Badwater Basin stands today. Named Lake Manly(*) by geologists, it disappeared 10,000 years ago.

Badwater Basin is 282 feet below sea level so any water that reaches it can only evaporate yet the evaporation rate is so high that the basin is a salt pan. Occasionally — decades apart — there’s enough rain to make a shallow lake.

Badwater Basin in normal times, Dec 2018 (photo from Wikimedia Commons)

In the past six months California has had two unusual rain events. On 20 August 2023 Hurricane Hilary dumped 2.2 inches and caused Lake Manly to re-form in place. (The deluge also closed the Death Valley National Park for two months.) Amazingly the lake persisted through the winter.

Lake Manly, Death Valley, December 2023 (photo from Wikimedia Commons)

And then the Atmospheric River event of 4-7 February dumped 1.5 more inches of rain. Lake Manly grew to a depth of 1 to 2 feet so in mid-February the National Park Service opened it to kayaking.

video embedded from Associated Press on YouTube

The last time the lake formed, in 2005, it lasted only about a week. This time NPS estimates it’ll be gone — or at least too shallow for kayaks — by April.

So if you want to kayak in Death Valley, get out there now before Badwater Basin returns to normal.

Lake Manly typically looks like this in Badwater Basin, (photo from 2010 at Wikimedia Commons)

Read more here at ABC News: An ancient lake has reemerged at Death Valley National Park.

p.s. From Wikipedia: “The lake was named in honor of William Lewis Manly, who rescued immigrants from Death Valley in 1849.”

Solstice Begins the Shortest Season

December sunrise in Pittsburgh (photo by Kate St. John)

21 December 2023

When the sun stands still tonight at 10:27pm Eastern Time we’ll experience the shortest day of the year and begin the shortest season as well.

Regardless of the weather we change seasons four times a year based on astronomical events: December solstice, March equinox, June solstice, September equinox. Since these events occur at the same moment everywhere on Earth, each of the four seasons lasts the same amount of time for everyone. This is easiest to see on the Seasons page at A screenshot of Pittsburgh at 6am today is shown below.

Current and next seasons in Pittsburgh before the winter solstice (screenshot from

If you don’t like winter, the Northern Hemisphere has the best arrangement. Our astronomical seasons from shortest to longest are:

  • Winter = 88 days, 23 hrs, 39 mins (shortest)
  • Autumn = 89 days, 20 hrs, 37 mins
  • Spring = 92 days, 17 hrs, 44 mins
  • Summer = 93 days, 15 hrs, 52 mins (longest)

Climate change guarantees that winter is the shortest weather season, too. Winter was 21% of the year in 1952 but will take up only 9% of the year by the end of this century.

Average seasonal lengths in Northern Hemisphere, information from

So I’m not counting on a white Christmas.

Read more about the weather-based lengths of the seasons at:

Getting Ready for More Landslides

Landslide by the Bridle Trail in Schenley Park, July 2019 (photo by Kate St. John)

12 December 2023

Spring is landslide season in Pittsburgh. Winter is a good time to get ready for it and there’s no time like the present. With climate change increasing Pittsburgh’s rainfall and downpours, our dissolve-in-water bedrock is getting wet faster.

This morning the Pittsburgh Post-Gazette reported that, thanks to a $10 million federal grant, the City of Pittsburgh is about to begin two landslide mitigation projects along city streets on Mount Washington and is putting a third one out to bid.

Thankfully there is money, though not a lot of it, for municipalities to prevent landslides on our roads, but if you live above a landslide and you own the land that slid you’re out of luck. The slide eventually takes your house with it.

video embedded from KDKA, April 2022

Pittsburgh is especially prone to landslides because of our geology.

Two natural conditions occurring in western Pennsylvania are most responsible for landslide problems throughout the area. First, in many places the bedrock consists mainly of shales and claystones. The primary culprit is a thick, 40- to 60-foot rock layer called the Pittsburgh red beds.

[Red bed]rock rapidly falls apart in water and tends to lose strength with each seasonal freeze-thaw and wet-dry cycle. Water that collects in the rock has little chance to drain and subsequently helps make the slope unstable from the inside out.

The second naturally occurring condition responsible for landslides is western Pennsylvania’s landscape, which is dominated by steep hills and valleys.

[Hillside] soils normally are stiff but very prone to downhill movement. This movement normally is imperceptibly slow. During the spring, however, the soil often becomes very wet from thawing snow and spring rains and the creeping can accelerate into a full-blown landslide.

Pittsburgh Geological Society: Landsliding in Western Pennsylvania

It is easy to find red bed outcrops on our hillsides. Here’s one in Schenley Park where there used to be topsoil but the red bed, formerly beneath the surface, eroded and left this tree on stilts.

Pittsburgh redbed rock eroded away from tree roots, Schenley Park (photo by Kate St. John, 2020)

A closer look at the red bed rock shows that it broke into tiny pieces — little crumbles — when it got wet. My foot is in the photo for scale.

Pittsburgh redbed rock crumbles into tiny pieces when wet (photo by Kate St. John, my boot shown for scale)

The location of these photos is marked on a Google topo map of Schenley Park below. Notice how steep the hillside is where the red bed is exposed. Uh oh!

Schenley Park topo map with arrow pointing to location of redbed photos (map screenshot from Google Maps)

Because of the prevalence of Pittsburgh red bed rock there are landslide problems throughout Allegheny County. Click here or on the map image below to see the details. Keep in mind that the colors red and orange are bad. The only safe color is yellow.

screenshot of Allegheny County from the Allegheny County Landslide Portal

And just for emphasis, check out this video of a house that slide down the hill in 2019.

video embedded from WTAE Pittsburgh on YouTube, 22 Feb 2019

El Niño Snows in DC But Not Pittsburgh

Snow on sweetgum seed balls, 17 Dec 2020 (photo by Kate St. John)

27 November 2023

Last week a friend remarked on the wide variety of winter forecasts being touted for Pittsburgh from “Swamped With Snow” to “No Skis in Our Forecast.” How could the predictions be so different? I think it’s the Beltway effect.

Right now the world is in an El Niño year of warm sea surface temperatures in the central and eastern Pacific at the equator and along the coasts of Ecuador and Peru.

Sea surface temperatures during 1997 El Niño (map from Wikimedia Commons)

According to Wikipedia, this warming causes a shift in the atmospheric circulation with rainfall becoming reduced over Indonesia, India and northern Australia, while rainfall and tropical cyclone formation increases over the tropical Pacific Ocean. El Niño seriously affects South American weather and ripples out to North America as well. The U.S. seasonal outlook, Dec 2023 to Feb 2024, shows higher temperatures in the north and wetter weather in the south this winter.

Seasonal temperature and precipitation outlooks for the U.S., Dec 2023-Feb 2024 (maps from NOAA)

Of course this affects snowfall. El Niño’s winter history in 1959-2023 shows more snow in some places (blue color) and a lot less in others (brown color). Interestingly, Pittsburgh is in the Less Snow category while Washington, DC has More Snow than usual.

Snowfall during all El Niño winters (January-March) compared to the 1991-2020 average (after the long-term trend has been removed). Blue colors show more snow than average; brown shows less snow than average. NOAA map, based on ERA5 data from 1959-2023 analyzed by Michelle L’Heureux.

News organizations have a big presence in the DC Beltway area and write stories for the region. Some weather stories originate there and cross the Appalachians but when the news gets to Pittsburgh it might not apply to us. The typical example is when 2 feet of snow are forecast for D.C. and hardly any falls here. I think of this as the (DC) Beltway news effect.

So when we hear dire predictions for Pittsburgh’s winter this year I plan to wait rather then worry. My guess is that we’re likely to have rain.

Raindrops on twig (photo by Kate St. John)

I sure hope the temperature doesn’t hover near freezing when it rains. Fingers crossed that we’ll be fine.

Glaze ice in Pittsburgh (photo by Kate St. John)

Read more about snow and El Niño at NOAA’s S(no)w pain, S(no)w gain: How does El Niño affect snowfall over North America?

It’s Official: We’re Warmer Than 10 Years Ago

21 November 2023

Once a decade USDA crunches the past 10 years of actual temperatures across the U.S. to calculate the growing season for each location. What they found this time is that 2010-2020 was so much warmer that the plant hardiness zones moved north. Again.

In Pennsylvania we lost our coldest zone and gained a warmer one. The Average Annual Extreme Minimum Temperature — the worst freeze that can happen to a plant — used to be -20 to -15 F (Zone 5a) in Warren and McKean Counties. Both lost that colder zone and parts of Warren jumped two zones.

Meanwhile, southeastern Pennsylvania’s temperature span rose 5 degrees and jogged the Philadelphia area out of 7b into Zone 8a. That means you can grow some pretty exotic stuff in Philadelphia now.

NPR interviewed Megan London, a gardening consultant from Hot Springs, Arkansas whose region made the same jump as Philadelphia.

In the new map, London’s region in central Arkansas has moved from zone 7b to zone 8a. What that means for her is that she’s now considering growing kumquats, mandarin oranges, and shampoo ginger, a tropical plant.

NPR: ‘It feels like I’m not crazy.’ Gardeners aren’t surprised as USDA updates key map

This year’s heat in the eastern U.S. was a taste of the future. Watch an early Leaf Out — as much as 20 days ahead of schedule — creep up the map.

Spring leaf index anomaly animation for 2023 (map from USA National Phenology Network)

Compare the old and new plant hardiness maps for the entire U.S. Find the plant hardiness zone for your area on the USDA Plant Hardiness webpage.

(maps from USDA Plant Hardiness webpage and the USA National Phenology Network)

Leaf Peeping and Patchy Frost Prediction

Bright red maple leaf near Phipps Conservatory, 16 October 2023 (photo by Kate St. John)

21 October 2023

Fall color’s peak in southwestern Pennsylvania used to be around the 12th of October but climate change has pushed it later, closer to the 21st, as you can see in the PA fall foliage prediction for 19-25 October.

PA fall color prediction for 19-25 Oct 2023 (map from PA DCNR)

This week I found bright leaves on red maple trees, at top, and yellow on buckeyes and hickories.

Schenley Park leaves are yellow and green on 16 October 2023 (photo by Kate St. John)
Yellow and orange maple leaves, Frick Park, 18 October 2023 (photo by Kate St. John)

Frick and Schenley are dominated by oaks whose color will peak in the next two weeks. Meanwhile their few red maples turned red from the top down and have lost their leaves in the same order. The maples are gorgeous up close but you can’t see them from a distance because the tops are bare.

The top of this red maple is almost bare, 16 October 2023 (photo by Kate St. John)

Tomorrow night the northwest wind will bring migrating birds overnight and patchy frost on Monday morning.

This is the week to go leaf peeping.

(credits are in the captions)

Birds Take a Taxi to Correct For Climate Change

Male European pied flycatcher (photo from Wikimedia Commons)

9 October 2023

Birds like the European pied flycatcher (Ficedula hypoleuca) that winter in the tropics and southern hemisphere do not use weather clues to tell them when to fly north in the spring. Instead they cue on changing day length and return at the same time every year. But as Earth’s climate changes, spring comes weeks earlier than it used to and their migration timing is out of sync. Scientists in the Netherlands decided to give a few lucky birds a lift (a Lyft?) to Sweden and it made all the difference.

Pied flycatchers prefer to nest in or near oak trees where their nesting season is timed to correspond with the peak of caterpillar season. Unfortunately, spring is two weeks earlier now in the Netherlands, pied flycatchers arrive too late and have locally experienced a 90% decline.

Female European pied flycatcher carrying caterpillars (photo from Wikimedia Commons)

The old timing of Netherlands’ spring is now found in southern Sweden so scientists at University of Groningen in the Netherlands and Sweden’s Lund University decided to see what would happen to migration and nesting success if a few pied flycatchers were transported (by car!) from the Netherlands to suitable habitat in Sweden.

Anthropocene Magazine reports, “For three springs, starting in 2017, scientists from the University of Groningen in the Netherlands and Sweden’s Lund University caught newly-arrived Dutch female pied flycatchers and drove them by car to a nesting spot 570 kilometers (354 miles) away in southern Sweden that was already home to other pied flycatchers.”

Range of European pied flycatcher (map from Wikimedia Commons)

The experiment was wonderfully successful. The Netherlands’ females were in sync with the food supply and were twice as prolific as their Swedish counterparts who were locally out of sync. After spending the winter in Africa the former-Netherlands females returned to Sweden and so did their offspring!

Later the research team proved that migration timing is genetically inherited in European pied flycatchers by taxiing a few eggs laid in the Netherlands to Swedish nests. Those offspring returned to Sweden the following spring on the Netherlands timing.

Taxi service cannot be the answer to out of sync migration but birds are adapting on their own. During the study, banding still continued at Netherlands nests and some of those youngsters were found nesting in Germany, halfway to Sweden. They flew there on their own.

Read more about the taxi ride experiment in Anthropocene Magazine: For some birds, a “taxi” helps recalibrate out-of-sync migrations.

(photos and map from Wikimedia Commons; click on the captions to see the originals)

The Heat Loop

Hot weather sunset (photo from Wikimedia Commons)

26 July 2023

The weather is hot and getting hotter. Excessive heat plagued the West, Texas and Florida and now, in the next 6-10 days, the heat will move southeast with soaring temperatures at 100°F+.

U.S. 6-10 day temperature outlook, 31 July – 4 August as of 7/25/2023 (map from NWS)

It’s not just the air that’s hot, the ocean is too. This timelapse video from Colin McCarthy @US_stormwatch shows ocean temperature anomalies from 22 February to 21 July. The hottest colors — the highest above normal — are off the Pacific coast of South America and in the North Atlantic near Newfoundland.

Warming water off the coast of South America is the developing El Niño, part of the cyclical El Niño–Southern Oscillation (ENSO) that affects weather and climate around the world.

The real surprise is off the coast of Newfoundland where Colin McCarthy says “The North Atlantic is in uncharted territory. The entire ocean basin is a record-smashing 1.5°C (2.7°F) above normal.”

Both are easier to see in this static map from NOAA.

NOAA sea surface temperature anomaly (partial map) as of 24 July 2023, 0600 EDT

Hot water makes the air hot as Newfoundlanders can tell you. Summers are usually so cool there that only 1 in 5 households in St John’s, NL have air conditioning, at least as of 2019. That is probably changing this summer as temperatures soar into the 90s.

Hot water makes hotter air makes hotter water in an endless feedback loop.

With El Niño on top of climate change I don’t think it will end well.

p.s. Today’s news Florida ocean records ‘unprecedented’ temperatures similar to a hot tub!

(photo and map credits are in the caption; click the links to see the originals. The Heat Loop diagram is by Kate St. John)

Drought: The Long and Short of It

View of South Mountain from Queen Creek, AZ (photo from Wikimedia Commons)

12 July 2023

Short term:

Last Friday, 7 July, Pennsylvania was placed under a statewide drought watch by the PA Department of Environmental Protection. They evaluated four factors to make the decision: precipitation, surface water flow, groundwater level, and soil moisture. The most worrisome was low groundwater in 16 counties and a 90-day rain deficit in Elk and Warren.

And then it rained in central and eastern PA and the Drought Condition map changed. Most of the state is now in the green (good) or yellow zone. Except for low groundwater in 14 of our 67 counties, the drought appears to be short term because a good rain can clear it up. See the Before and After, July 9 and 11, in this slideshow.

USGS Pennsylvania Drought Condition monitoring as of July 9 and 11, 2023

Long term:

Meanwhile, Arizona is not in a drought right now but it’s a desert, its water supply is limited, and it suffered a long term drought for many years. Water allocation has to be planned in Arizona so they won’t run out. This prompted Phoenix put the brakes on development last month in places that rely on ground water.

Arizona will not approve new housing construction on the fast-growing edges of metro Phoenix that rely on groundwater thanks to years of overuse and a multi-decade drought that is sapping its water supply. …

Officials said developers could still build in the affected areas but would need to find alternative water sources to do so — such as surface or recycled water.

Driving the state’s decision was a projection that showed that over the next 100 years, demand in metro Phoenix for almost 4.9 million acre-feet of groundwater would be unmet without further action, Hobbs said. An acre-foot of water is roughly enough for two to three U.S. households per year. …

Hobbs added that there are 80,000 unbuilt homes that will be able to move forward because they already have assured water supply certificates within the Phoenix Active Management Area, a designation used for regulating groundwater.

TribLive: Drought, water overuse prompt Arizona to limit construction in some fast-growing parts of Phoenix

I’ve marked up this Google map of Phoenix to show the fastest growing areas circled in red.

Map of Phoenix, AZ metro with circles added: 5 fastest growing suburbs (screenshot from Google Maps)

Back in the 1990s I had a friend in the City of Phoenix’s economic development department who was proud to predict that, based on the city’s projected level of development, they had 75 years of water. In other words, they were OK until approximately 2070. My thought at the time was “Only 75 years?? Then what??”

Now we know. It took only 30 years to put the brakes on.

p.s. Phoenix, in Maricopa County, is one of the fastest growing areas of the U.S.; Maricopa grew 20.55% since 2010. Being from Pittsburgh, where Allegheny County grew 2.89% in the same time period, I marveled at the notion of 80,000 unbuilt homes.

(photo and map credits are in the captions, click on the links to see the originals)