Why Should I Care About Climate Trends?

  • Changes in air temperature and precipitation patterns will shift habitat ranges of native species, making these systems more vulnerable to exotic invaders, pathogens, insects, and new diseases.
  • Heat stress will impact the health of elderly and children.
  • Farmers may enjoy the short-term benefits of a longer growing season, but variable timing and duration of precipitation may diminish less hardy, adaptable, or cold-weather crops.
  • Droughts and floods in other parts of the country will likely increase food prices in our local grocery stores.
  • Heavy rains will cause damage to habitat and infrastructure, including washed out roads and collapsed culverts.
  • Warmer winter temperatures that replace snow with sleet or freezing rain will make ski conditions poor, forcing ski resorts to expend more money making their own snow.
  • Shorter lake ice duration will mean a shorter season for ice fishing, skating, and snowmobiling.
  • Treasured local or regional winter events will also likely be cancelled due to poor snow conditions or unsafe lake ice.

How Can I Help?

Air Pollutant Trends

Burning Fuels Causing a Warming Planet

We rely on the burning of fossil fuels (i.e., gasoline, coal, and natural gas) for nearly all aspects of our everyday lives.

This heightened energy demand for and use of these finite resources over the last century has introduced an excess of noxious gases to the atmosphere.

Some of these gases (e.g., carbon dioxide, methane, and nitrous oxide), also known as greenhouse gases, are responsible for trapping reflected heat from the earth’s surface.

This process is vital to maintaining a habitable planet, but excess greenhouse gases in the atmosphere enhances this effect by trapping more heat and increasing air temperatures globally.

Warmer air temperatures impact rain and snow patterns, sea level rise, and species migrations.

Acid Rain Impact on Kezar Lake Watershed

Fossil fuel combustion also emits sulfur dioxide and nitrogen oxides to the atmosphere. These gases react with water vapor, oxygen, and other gases in the atmosphere to form sulfuric and nitric acids, which fall on water and land surfaces as acid rain.

Acid rain lowers the pH of aquatic and terrestrial systems, causing reduced reproductive capacity of sensitive aquatic organisms, lower body weight of fish, decreased species diversity, and forest mortality.

Substantial effort was made to reduce acid rain deposition through the 1970 Clean Air Act, which established national ambient air quality standards for controlling these noxious emissions.

While emissions have decreased and the damaging short-term effects of acid rain have been minimized, many waterbodies are still recovering from the long-term effects of acidification.

In particular, parts of the northeastern United States have thin soils with granite geology that lack carbonates, a key component of a system’s buffering capacity or ability to neutralize acidic compounds.

We see this in streams of the Kezar Lake watershed where low-pH rain (5.0) temporarily decreases the pH of surface waters. These swings in pH create stressful environments for sensitive aquatic organisms.

Air Temperature Trends

Climate change is expected to increase global air temperatures, an effect that we have already observed in the last century. An important point to understand about climate change is the difference between “climate” and “weather.” Climate change observations and predications are based on “climate,” which is long-term averages of weather observations across regional or global space. For example, the State of Maine has seen a 3 °F increase in annual air temperatures in the last century. Local weather observations may deviate from this general trend from season to season or year to year, depending on a suite of local variables. For the Kezar Lake watershed, we used the North Conway weather station to track changes in air temperature since 1959.

Annual Air Temperatures in North Conway, NH

We are experiencing 8 °F warming in minimum air temperatures and 1 °F warming in average air temperatures since 1959.

Average and minimum annual air temperatures have warmed by about 1 °F and 8 °F, respectively, near North Conway, NH. Maximum annual air temperatures have remained stable. In 1960, the minimum, average, and maximum annual air temperatures were 4 °F, 44 °F, and 80°F, respectively. This compares with higher minimum, average, and maximum annual air temperatures observed in 2012: 13°F, 47 °F, and 82°F.

Data taken from the NOAA National Climatic Data Center for station CONWAY 1 N, NH US (ID# GHCND:USC00271732).for 1959-73 and station NORTH CONWAY, NH US (ID#GHCND:USC00275995). Mann-Kendall trend tests were performed on datasets with 10 or more years of data. Statically-significant trends are shown as dotted trend lines.

Extreme Heat Days in North Conway, NH

We are not experiencing any significant trends in extreme heat days due to year-to-year variability. The northeast will likely not experience as dramatic an increase in extreme heat days as other parts of the country.

As air temperature rises, we can expect to see more extreme heat days. However, the North Conway weather station data since 1959 show no trend in the number of days per year with air temperatures over 90 °F. In fact, the number of extreme heat days seems to have declined in the last decade, though 2018 had the most extreme heat days since 2001. Several climate models show that the northeast will not experience as dramatic an increase in extreme heat days as the southern and middle portions of the United States.

Data taken from the NOAA National Climatic Data Center for station CONWAY 1 N, NH US (ID# GHCND:USC00271732).for 1959-73 and station NORTH CONWAY, NH US (ID#GHCND:USC00275995). Mann-Kendall trend tests were performed on datasets with 10 or more years of data. Statically-significant trends are shown as dotted trend lines.

Extreme Cold Days in North Conway, NH

We are experiencing 20 less extreme cold days below 0°F each year compared to 1959. Winters are warming faster than summers.
As air temperature rises, we can expect to see less extreme cold days. As expected, the North Conway weather station data since 1959 show a statistically significant decrease in the number of days per year with air temperatures below 0 °F. The first half of the record shows the number of extreme cold days around 25-30, but the latter half shows the number of extreme cold days declining to 10-15.

Data taken from the NOAA National Climatic Data Center for station CONWAY 1 N, NH US (ID# GHCND:USC00271732).for 1959-73 and station NORTH CONWAY, NH US (ID#GHCND:USC00275995). Mann-Kendall trend tests were performed on datasets with 10 or more years of data. Statically-significant trends are shown as dotted trend lines.

Precipitation Trends

Warming air temperatures have impacted rain and snow patterns across the globe. In Maine, total annual precipitation has increased by 6 inches (13%) since 1895. Snowpack duration has decreased by two weeks since 1895 across Maine. For the Kezar Lake watershed, we used the North Conway weather station to track changes in precipitation since 1959.

Annual Precipitation in North Conway, NH

Annual precipitation has been highly variable since 1959 with no discernible patterns.

In North Conway, total annual precipitation has fluctuated greatly, but without any trend since 1959. However, three years (1996, 2005, and 2008) saw total annual precipitation above 60 inches. These were extremely wet years impacted by major storms. Total annual precipitation seems to be decreasing in the last decade, but may be rebounding with a wetter 2017 and 2018.

Data taken from the NOAA National Climatic Data Center for station CONWAY 1 N, NH US (ID# GHCND:USC00271732).for 1959-73 and station NORTH CONWAY, NH US (ID#GHCND:USC00275995). Mann-Kendall trend tests were performed on datasets with 10 or more years of data. Statically-significant trends are shown as dotted trend lines.

One Inch Rain Events in North Conway, NH

The number of days per year with greater than 1 inch of rainfall has been highly variable since 1959 with no discernible patterns.

Climate change will likely cause more frequent precipitation events. For North Conway, the number of days per year receiving greater than 1 inch of rain has been highly variable; however, the last decade shows multiple years with greater than 12 days per year with 1 inch or more of rain recorded.

Data taken from the NOAA National Climatic Data Center for station CONWAY 1 N, NH US (ID# GHCND:USC00271732).for 1959-73 and station NORTH CONWAY, NH US (ID#GHCND:USC00275995). Mann-Kendall trend tests were performed on datasets with 10 or more years of data. Statically-significant trends are shown as dotted trend lines.

Wettest Day of Year in North Conway, NH

The amount of rainfall on the wettest day each year has been highly variable since 1959 with no discernible patterns.

The intensity of extreme rain events is illustrated by finding the day from each year with the largest amount of precipitation. Since Maine has an extensive coastline, extreme precipitation events are often related to Atlantic storms. For instance, the extreme precipitation day for 1960 (5.5 inches) coincides with Hurricane Donna. The wettest day of the year precipitation amounts varied considerably throughout the record for North Conway, and no trend was observed.

Extreme precipitation events are increasing in frequency and duration, particularly along the coast and in the western mountains. More frequent and intense rain events flush excess nutrients from the landscape to receiving waterbodies, including Kezar Lake, which can fuel algal production. Larger flow volumes also threaten infrastructure, including road crossings and culverts.

Data taken from the NOAA National Climatic Data Center for station CONWAY 1 N, NH US (ID# GHCND:USC00271732).for 1959-73 and station NORTH CONWAY, NH US (ID#GHCND:USC00275995). Mann-Kendall trend tests were performed on datasets with 10 or more years of data. Statically-significant trends are shown as dotted trend lines.

Snowfall Accumulation in North Conway, NH

We are experiencing 35 inches less of annual snowfall accumulation since 1959.

As air temperatures increase, climate change models predict less snowfall and reduced snowpack duration. Maine has already shown a statistically significant trend of decreased annual snowfall between 1950 and 2000. For North Conway, total annual snowfall has declined from about 105 to 70 inches of snowfall per year since 1959.

Data taken from the NOAA National Climatic Data Center for station CONWAY 1 N, NH US (ID# GHCND:USC00271732).for 1959-73 and station NORTH CONWAY, NH US (ID#GHCND:USC00275995). Mann-Kendall trend tests were performed on datasets with 10 or more years of data. Statically-significant trends are shown as dotted trend lines.

Ice-Out Trends

Ice-out data has been collected for Kezar Lake since 1901, providing over a century of information about changes in the seasonal duration of winter snowpack and ice. Ice-out refers to the day when all ice covering Kezar Lake has broken up and melted. This marks the beginning of spring when the entire lake is exposed to direct sunlight, which stimulates lake productivity and drives the critical process of spring turnover.

Kezar Lake Ice-Out Dates

Annual ice-out dates have been highly variable since 1901, but shows a possible earlier ice-out trend in the last few decades.

Although some years within the last decade showed abnormally early ice-out dates, no statistically significant trend was found for all data since 1901. The increasing variability and abnormally early ice-out dates within the last few decades should be monitored closely in the future to confirm the trend. Early ice-out is directly linked to warming air temperatures and changes in seasonality.

Mann-Kendall trend tests were performed on annual ice-out dates (based on Julian calendar) to determine trends over time. Although some years within the last few decades showed abnormally early ice-out dates, no statistically significant trend was found for all data since 1901.

Projections

  • Maine can expect an additional 3.0-5.0 °F increase in annual air temperatures by 2050; these temperature increases will largely occur in winter and will lengthen the growing season by an additional 2 weeks.

  • Western Maine will experience an increase of 2.5 to 6.5 days when the heat index is greater than or equal to 95 °F by 2050.

  • Precipitation in western Maine will increase 5-6% by 2050, most of which will fall in summer and fall.

  • Maine will experience more frequent and intense storm events (defined as greater than 2” of rain within 24 hours). This is indirectly linked to changes in sea surface temperature in the North Atlantic and melting sea ice in the Arctic.

  • Western Maine, will experience a 20-40% decline in annual snowfall by 2054. Just as the growing season is predicted to increase by 2 weeks, so the duration of snowpack will decrease by 2 weeks by 2050.

  • It is very likely that while total snowfall will decline, snow that does fall will likely occur as extreme events (e.g., nor’easters) with significant accumulations in a few, single events.

Local Climate Trends Summary

As a result of human-induced climate change (i.e., our fossil fuel combustion), the Kezar Lake watershed is already experiencing a 1 °F and 8 °F increase in average and minimum annual air temperatures, respectively, a decrease in the number of extreme cold days (sub-zero), and a decrease in annual snowfall. Ice-out on Kezar Lake may be arriving earlier over the last several decades. Maine climate projections only show these trends worsening in the next century, which will impact the environmental, economic, and social well-being of the area.

References for Climate Trends

Boeck, M., Jackson, R., and H. Shaftel. Global Climate Change Temperature. NASA. July 28, 2015. http://climate.nasa.gov/interactives/climate-time-machine

Fernandez, I.J., C.V. Schmitt, S.D. Birkel, E. Stancioff, A.J. Pershing, J.T. Kelley, J.A. Runge, G.L. Jacobson, and P.A. Mayewski. “Maine’s Climate Future: 2015 Update.” Orono, ME: University of Maine (2015): 24 pp. www.climatechange.umaine.edu/research/publications/climate-future

Horton, R., G. Yohe, W. Easterling, R. Kates, M. Ruth, E. Sussman, A. Whelchel, D. Wolfe, and F. Lipschultz, 2014: Ch. 16: Northeast. Climate Change Impacts in the United States: The Third National Climate Assessment, J. M. Melillo, Terese (T.C.) Richmond, and G. W. Yohe, Eds., U.S. Global Change Research Program, 16-1-nn. http://nca2014.globalchange.gov/report/regions/northeast

Hodgkins, Glenn A., Ivan C. James, and Thomas G. Huntington. “Historical changes in lake ice‐out dates as indicators of climate change in New England, 1850–2000.” International Journal of Climatology 22.15 (2002): 1819-1827.

IPCC [Core Writing Team, R.K. Pachauri and L.A. Meyer (eds.)]. “Climate Change 2014: Synthesis Report. Contribution of Working Groups I, II and III to the Fifth Assessment Report of the Intergovernmental Panel on Climate Change.” IPCC, Geneva, Switzerland: (2014): 151. http://www.ipcc.ch/pdf/assessment-report/ar5/syr/SYR_AR5_FINAL_full.pdf

NOAA. Monthly Summaries of the Global Historical Climatology Network – Daily (GHCN-D). COOP:275995 & 271732. NOAA National Climatic Data Center. July 21, 2015.