Four years ago today, I started writing this blog and it has been both an amazing and rewarding journey.
Initially begun as a way to deepen and share my knowledge about weather and climate change, this blog has allowed me to expand on my interests and concerns in ways that I never thought possible four years ago. This past year, I developed a selection of slide presentations about climate change and have spoken at a variety of venues, including a national conference. It has also introduced me to many wonderful people working in this fascinating field. Looking ahead, I am hoping to add some video content to the blog over the next few months. So, stay tuned!
Today is the Autumnal Equinox, the first day of fall in the northern hemisphere. The new season officially began at 8:21 UTC, which is 4:21 AM Eastern Daylight Time.
The astronomical seasons are a product of the tilt of the Earth’s axis – a 23.5° angle – and the movement of the planet around the sun. During the autumn months, the Earth’s axis is tilted neither toward nor away from the sun. This position distributes the sun’s energy equally between the northern and southern hemispheres.
Since the summer solstice in June, the arc of the sun’s apparent daily passage across our sky has been moving southward and daylight hours have been decreasing. Today, it crossed the equator and we have approximately equal hours of day and night. The word “equinox” is derived from Latin and means “equal night”.
With the sun sitting lower in the sky and daylight hours continuing to shorten, Autumn is a season of falling temperatures. According to NOAA, the average high temperature in most US cities drops about 10°F between September and October.
Earth’s solstices and equinoxes. Image Credit: NASA
The Earth’s axis is tilted neither toward nor away from the sun on the Equinox. Image Credit: NASA
Our global temperature continued its upward trend last month with August 2015 not only marking the warmest August on record, but also closing out the warmest meteorological summer ever recorded for the entire planet.
According to a report by NOAA’s National Centers for Environmental Information, Earth’s combined average temperature for August – over both land and sea surfaces – was 61.68°F, which is 1.58°F above the 20th century average. It surpassed the previous record set just last year by 0.16°F and was the sixth month this year to break a monthly temperature record. It also marked the 366th consecutive month that our global temperature was above its long-term norm.
Rising ocean temperatures compounded by El Niño conditions in the tropical Pacific helped fuel August’s record warmth. The globally averaged sea surface temperature for the month was 1.40°F above the 20th century average, which makes it the highest temperature on record for any month. The previous record was set in July 2015.
The three-month period of June, July and August – known as the meteorological summer in the northern hemisphere – was also a record breaker! NOAA reports that Earth’s combined average temperature for the season – over both land and sea surfaces – was 1.53°F above the 20th century average. That is 0.20°F above the previous record that was set last summer.
While heat dominated most of the planet from June to August, some places were particularly warm, including much of Europe. Austria, France, and Switzerland each experienced their second warmest summer on record and Germany posted its third warmest. Even the southern hemisphere, where it was austral winter, saw warmer than usual conditions. Argentina experienced its warmest winter since national record keeping began there in 1961.
Here in the contiguous US, the summer of 2015 was our 12th warmest on record. While some of the central states saw average to below average temperatures, many of the western states were exceptionally warm. In fact, Oregon and Washington each experienced their warmest summer on record.
Year to date, the first eight months of 2015 were the warmest of any year on record. That puts 2015 on track to becoming Earth’s warmest year ever recorded. Global temperature records date back to 1880.
2015 is well on its way to becoming Earth’s warmest year on record. Credit: NOAA
The famous author Mark Twain is credited with the phrase, “If you don’t like the weather in New England now, just wait a few minutes.” While his focus was on the northeastern United States, this saying can be true of many places. Coastal Alaska, for example, is famous for its highly changeable weather conditions.
Visiting the town of Homer, AK on the Kenai Peninsula, I came across a shop where they seem to take the essence of Mr. Twain’s saying to heart. Framed by their back window overlooking Kachemak Bay, they humorously offer a highly visual and continuously updated description of local weather conditions. It seems that sometimes a picture really can be worth a thousand words.
View from the back window of a shop in Homer, AK. Photo Credit: The Weather Gamut.
Many things in nature are adapted to certain climate conditions. That said, some are choosier than others. Giant Sequoia trees, the largest living organisms on the planet, need a “Goldilocks” type of environment to grow and reproduce. Visiting Sequoia National Park recently, I had the opportunity to learn more about the climate requirements of these amazing trees.
Needing conditions that are not too hot and not too cold, as well as not too wet and not too dry, Giant Sequoias grow naturally in only one place on Earth. That unique place is a narrow band about 70-miles long on the western slopes of California’s Sierra Nevada Mountains known as the Sequoia Belt. According to the National Park Service (NPS), these trees only grow at elevations between 5,000 and 7,500 feet. Temperatures above 7,500 feet are usually too cold and conditions below 5,000 feet are too dry. Within this limited range, about 75 groves reveal where conditions for the massive trees are just right.
These ideal conditions are produced by a combination of weather and topography. When moisture-laden air from the Pacific runs into the Sierras, it rises and cools. On average, it cools about 3.6°F for every 1000 feet it rises. Since cooler air holds less moisture than warm air, the moisture is dropped as rain and snow over the mountains with precipitation amounts generally increasing with elevation. While California is in the midst of a multi-year drought, the NPS says the area around Giant Forest (elevation 6400 feet) usually gets an average of 44 inches of precipitation a year. It also typically sees only one day a year with temperatures below 10°F.
Compared to other sites within a five mile radius, the average conditions in Giant Forest are perfect for the giant sequoias. Upslope, Emerald Lake (elevation 9200 feet) gets 59 inches in average annual precipitation and sees around ten days a year with temperatures below 10°F. Downslope, Ash Mountain (elevation 1700 feet), only sees about 26 inches of precipitation a year and the temperature reportedly never falls below 10°F.
Given the narrow natural range in which these giant trees are able to thrive, they face serious challenges from climate change. As temperatures increase, more precipitation is coming down in the form of rain instead of snow. This reduces the snowpack and the subsequent spring and summer melt water available to the trees during the region’s dry season. While the resilient mature sequoias – some are over 3000 years old – are not in immediate danger, researchers say these big trees were not made to withstand decades of drought. The younger trees – seedlings and saplings – on the other hand, face a more difficult struggle for survival. The drier conditions make it harder for them to develop robust root systems and also leave them more susceptible to wildfires, which are projected to increase.
Given the impressive age of some of these trees, they must have endured natural climate fluctuations in the past. This time, however, the human caused change is happening very quickly and is forecast to produce conditions unfamiliar to even these ancient giants. According to the US National Climate Assessment, the southwest – which includes California – is normally the hottest and driest part of the country, but climate change is making it even more so. The report shows that 2001 through 2010 was the region’s warmest decade on record with temperatures almost 2°F above historic averages. Looking ahead, it projects continued increases in average annual temperature and a decrease in precipitation. In the meantime, scientists continue to monitor and research the giant sequoias to better understand how they will react to our changing climate and to offer informed recommendations to evolving conservation strategies.
Below is a short video by The Redwoods and Climate Change Initiative (RCCI) on the impact of extended drought on Giant Sequoias. Oh, and in case you were wondering, Giant Sequoias (sequoiadendron giganteum) and Coastal Redwoods (sequoia sempervirens) are closely related, but are two different species.
It was hot in New York City this August. Everyday produced a high temperature above 80°F and eight days saw the mercury climb to 90°F or higher, which is twice the average number for August. Additionally, the month brought the city its first official heat wave in two years. With overnight lows also running mostly above normal, the city’s mean temperature for the month was 79°F, which is 3.8°F above average. This makes August 2015 the city’s 3rd warmest August on record.
On the precipitation side of things, August was very dry in the Big Apple. All told, the city received a mere 2.35 inches of rain in Central Park, which is 2.09 inches below average. On the latest report (8/25) from the US Drought Monitor, the NYC area is listed as “abnormally dry”.