The Weather Guys

Is climate change uniform across the globe?

Posted on December 2, 2024 by WeatherGuys Editor

As the map below shows, most land areas have warmed faster than most ocean areas, and the Arctic is warming faster than most other regions. Recent warming is much faster than the longer-term average, with some locations warming by 1 degree Fahrenheit or more per decade. Differences are most dramatic in the Arctic, where the loss of reflective ice and snow amplifies the rate of warming. (Image credit: NOAA Climate.gov, based on data provided by NOAA National Centers for Environmental Information)

Temperature is a fundamental indicator of a climate. Annual and seasonal temperatures patterns have a defining role in the types of animals and plants that reside in an ecosystem. Rapid changes in temperature can disrupt a wide range of natural processes. This is one reason we monitor temperature changes as a metric for global change. The National Oceanic and Atmospheric Administration’s National Centers for Environmental Information maintain a collection of climate data online at: www.ncei.noaa.gov

Concentrations of heat-trapping greenhouse gases, such as carbon dioxide, are increasing in the Earth’s atmosphere. This increase is due to anthropogenic activity. In response, the average temperatures at the Earth’s surface are increasing and are expected to continue rising. Though global temperature changes can shift the wind patterns and ocean currents, the regional warming is not uniform.

The observed global average surface temperature has risen at an average rate of 0.17°F per decade since 1901. Since 1901, the average surface temperature across our contiguous 48 states has similarly risen at an average rate of 0.17°F per decade. The average temperatures have risen more quickly since the late 1970s: from 0.32 to 0.51°F per decade since 1979. For the contiguous United States, nine of the 10 warmest years on record have occurred since 1998.

The changes across the globe show no uniform patterns in the rate of increase. The temperatures of the Arctic are rising two to four times faster than the global average. The Antarctic Peninsula has also experienced a similarly dramatic warming. Desert areas also warmed at rates exceeding the global average warming rate.

Of course, this regional variability makes the problem of accurately predicting how the associated changes in weather patterns across the globe will change in a warmer world even more difficult to solve. However, understanding such weather variability is absolutely critical to meeting the warmer future with in the least disruptive way.

Steve Ackerman and Jonathan Martin, professors in the UW-Madison department of atmospheric and oceanic sciences, are guests on WHA radio (970 AM) at noon the last Monday of each month. Send them your questions at stevea@ssec.wisc.edu or jemarti1@wisc.edu.

Category: Climate, History

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How and when do Madison lakes freeze?

Posted on November 25, 2024 by WeatherGuys Editor

The surface of a lake exchanges energy with the air above. Cold air cools the lake surface through energy exchanges with the atmosphere, determined by the weather above. As cool surface water cools, it becomes denser than the warmer water below and so the cooled water sinks. Water from below then rises to the surface where it begins to cool.

The Lake Mendota buoy project is a collaboration between the University of Wisconsin Limnology, Space Science and Engineering Center (SSEC) and Environmental Engineering. The buoy measurements provide researchers valuable information to better understand the biological process governing the health of the lake and the impact of human activity on water quality. The buoy is located approximately 1.5 km North East of Picnic Point.

What is unique about the H₂O water molecule is that as liquid water cools, its density increases until about 39°F (4°C). At that point, the colder water becomes less dense, stays at the surface, and continues to cool. Once the surface water cools to approximately 32°F, the water molecules crystallize into interlocking lattice-like patterns and ice is formed. For a lake surface to freeze, the entire lake needs to be at a temperature of 39°F; only then as the surface cools will the temperature of the liquid water at the surface remain less dense than the water below and thus float and begin to form ice. Shallower lakes usually freeze before deeper lakes since shallower lakes contain less water that needs to be cooled.

When a lake will freeze is not determined solely by cold autumn weather but also depends on the lake’s temperature throughout the year. If the lake warms more than average during the summer, it could take longer to cool because the entire lake must reach a temperature of 39°F. If you want to monitor Lake Mendota’s temperature (and other factors), data is provided to the public by the Lake Mendota Buoy (or David Buoy): https://metobs.ssec.wisc.edu/mendota/buoy, a service of UW-Madison.

A lake’s freezing date is the first date that most of the lake surface is estimated to be frozen. The Lake Mendota, Lake Monona, and Lake Wingra median freeze dates are December 20, December 15, and November 29, respectively.

Category: Meteorology, Seasons

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What is climate change?

Posted on November 19, 2024 by WeatherGuys Editor

Increased concentrations of GHGs from anthropogenic sources have increased the absorption of infrared radiation, enhancing the natural greenhouse effect. (Image credit: Center for Sustainable Systems (CSS), University of Michigan)

Climate can be defined as the collective state of the atmosphere for a given place over a specified interval of time. There are three parts to this definition: location, because climate can be defined for a globe, a continent, a region or a city; time, because climate must be defined over a specified period; and the collective state of the atmosphere, which includes averages and extremes of variables such as temperature, precipitation, pressure and winds.

Climate change is a long-term change in the average weather patterns that have come to define Earth’s local, regional and global climates.

Climate change can result from natural events, such as volcanic eruptions, asteroid impacts or changes in our sun’s energy output.

Climate change can also be caused by human activities. The building of cities is a well-documented example of inadvertent modification of a climate by human activities. The urban heat island effect refers to the increased temperatures of urban areas compared with a city’s rural surroundings. Several factors contribute to the relative warmth of cities, such as heat from industrial activity and the thermal properties of buildings and roads.

Since the 1800s, human activities have been the main driver of observed climate change, primarily due to the burning of fossil fuels such as coal, oil and gas. Burning fossil fuels generates greenhouse gases, which are transparent to solar radiation but absorb large amounts of terrestrial infrared radiation that results in warming the atmosphere.

Over the past two centuries, the global average surface temperature has increased noticeably. Currently, Earth is about 2.11 degrees Fahrenheit warmer than the late 19th-century preindustrial average. The 10 most recent years are the warmest on record. There is no debate about the cause of this warming trend; it has resulted from human activities, principally through emissions of greenhouse gases.

Category: Climate, History

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What is the National Weather Service?

Posted on November 12, 2024 by WeatherGuys Editor

The logos of the National Oceanic and Atmospheric Administration and the National Weather Service (Image credit: NOAA/NWS)

The National Weather Service, or NWS, is an office of the National Oceanic and Atmospheric Administration, NOAA, which sits in the U.S. Department of Commerce. The connection to the Department of Commerce is sensible – it’s estimated that one-third of the U.S. economy is sensitive to weather and climate.

The mission of the National Weather Service is to “provide weather, water, and climate data, forecasts, warnings and impact-based decision support services for the protection of life and property and enhancement of the national economy.”

The roots of the NWS go back to Feb 9, 1870, when U.S. President Ulysses S. Grant signed a joint resolution of Congress into law establishing the Weather Bureau of the United States. It was originally placed within the U.S. Army Signal Services’ Division of Telegrams and Reports for the Benefit of Commerce. Twenty years later, on Oct. 1, 1890 at the request of President Benjamin Harrison, Congress passed a law transferring the meteorological responsibilities of the Signal Service to the newly created U.S. Weather Bureau, housed in the Department of Agriculture. The Weather Bureau became the National Weather Service in 1970 with the creation of NOAA.

The NWS and NOAA are incredible public goods. The NWS provides weather forecasts, warnings, and climate data across the U.S. and exchanges that information with weather services around the globe. The NWS and NOAA weather observations and forecasts are publicly available at no cost. Their forecasts are accurate enough that we use them daily to schedule outdoor activities, adjust travel, wear clothes appropriate for conditions and plan for impending storms. These forecasts help to save lives.

Commercial weather companies use this public data along with private and proprietary weather data and models to create industry-specific weather forecasts. Publicly available and paid weather services complement one another and keep our nation informed and prepared for coming weather events.

Category: Uncategorized

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How unusual was our dry and warm October weather?

Posted on November 4, 2024 by WeatherGuys Editor

The National Weather Service in La Crosse says there have been precipitation deficits of 1 to 8 inches in Door County, with the greatest deficits of 4 to 8 inches south of Interstate 90. That has resulted in the dry and drought conditions for Wisconsin, Minnesota and Iowa. (*Image credit: NWS-La Crosse)*

Meteorologists often compare current temperature and precipitation measurements to “normal” values to interpret unusual weather. The weather data observed over the 30-year period between 1991 and 2020 are used to define “normal” or “average” weather. These normals are recalculated every 10 years. The normals are determined on annual, seasonal, monthly, daily and even hourly timescales. The maximum and minimum values also are tracked for each day of the year.

The weather that southern Wisconsin has experienced this October has been different from our normal October weather. Throughout most of October, we experienced very dry conditions. Prior to the storms that occurred on Oct. 30 and 31, the total precipitation across most of the state was less than 50% of the normal precipitation. This lack of precipitation throughout the month was alleviated during the final two days. Many areas in Dane County received over 3 inches of rain on Oct. 30 and 31.

Record warm temperatures were recorded in Madison on October 29: The high was 82 degrees Fahrenheit, tying the record high temperature for that day set in 1937 and making it only the second time we have hit 80 degrees or higher that late in the year. Also, the low temperature of 65 degrees that day set a record warm minimum temperature, breaking the old record of 63 degrees set in 1946. The National Weather Service at Green Bay also set high temperature marks: 82 degrees on Oct. 29 and 80 degrees on October 30 were new records.

The record temperatures were supported by strong winds from the south and southwest moving warm air northward. The lack of precipitation throughout most of the month has contributed to low soil moisture. These dry conditions also support warmer air temperatures.