Implications of Climate Change for Recreation in the United States
Sarah Nicholls, Bas Amelung and David Viner
Introduction to Climate Change
Purpose
The world’s climate is changing. According to the Intergovernmental Panel on Climate Change (IPCC,
2001):
Figure 1A TCI (January, 1961-1990, left) and 1B TCI (January, 2040-2069, right)
•The global average surface temperature has increased 0.6 ± 0.2°C since 1861;
•The 1990s were the warmest decade, and 1998 the single warmest year, since records began;
•Since the 1860s, global average sea level has risen 0.1 to 0.2 meters.
The purpose of the study was to identify the potential impacts of projected climate change on recreational
and general tourism activity in the United States over the next century, based on calculation of TCI comfort
levels as suggested by Mieczkowski. A detailed methodology is available from the authors upon request.
Results and Discussion
The TCI was calculated for every month for four time periods, the 1970s (1961-1990), the 2020s (20102039), the 2050s (2040-2069) and the 2080s (2070-2099). A single climate change scenario (A2A with the
HadCM3 GCM) was used. Figures 1 and 2 illustrate TCI levels across the entire United States in January (1)
and July (2) for the 1970s (A) and 2050s (B).
Global land and marine surface temperature, 1856-2004
(Source: Jones et al., 1999; Jones & Moberg, 2003)
Our exploration suggests that climate change will affect the climatic suitability of the United States for
general tourism and recreation activities over the next century. However, the projected changes between the
1970s and the 2050s vary by region and season.
While estimates vary depending upon the modeling procedures and assumptions used, climate change
scenarios suggest that global average surface temperature will increase by between 1.4 and 5.8°C between
1990 and 2100. Projections regarding global mean sea level indicate a rise of between 0.09 and 0.88 meters
over the same period. An increase in the frequency and intensity of extreme weather events (floods, droughts,
heat waves, etc.) is also expected (IPCC, 2001).
Causes of Climate Change
Figure 2A TCI (July, 1961-1990, left) and 2B TCI (July, 2040-2069, right)
The Earth’s climate system is a complex interaction of a number of components including the ocean,
atmosphere, ice masses and living organisms. Although the system is ultimately driven by solar energy,
changes to any of the components, or to their interactions with one another, can lead to a change in climatic
conditions. These changes can occur over a variety of time scales, from short term seasonal variations to
long-term (geological time scale) changes. Four key causes of climate change are:
Variations in solar output;
Milankovitch cycles – changes in the character of the Earth’s orbit around the Sun, and in its rotation, affect
the way in which energy from the Sun is distributed by season and by latitude;
Volcanic pollution – explosive volcanic eruptions can inject large quantities of dust and sulphur dioxide
high into the atmosphere. This volcanic pollution results in a substantial reduction in incoming solar energy;
The greenhouse effect – once solar energy has reached the Earth's surface, it is absorbed, thereby warming
the land and oceans, and is then re-emitted. The amount of heat re-emitted and eventually lost to space must
equal the amount gained from the Sun if the temperature of the planet is to remain constant. Greenhouse
gases absorb the outgoing terrestrial energy, trapping it near the Earth's surface and causing increased
warming. This is the ‘greenhouse effect.’ Without it the planet would be too cold to support life as we know
it. Human society, however, through energy generation, land use change and other processes, has produced a
substantial increase in the amount of greenhouse gases in the atmosphere, thereby enhancing the
natural greenhouse effect. It is feared that this continuing change will lead to a major shift in global climate,
as described above.
The Tourism Climatic Index
The Tourism Climatic Index (TCI) was developed by Mieczkowski (1985) as the first ever evaluation of the
suitability of the world’s climates for the purposes of general recreation and tourism activity. The index is
based on monthly means for seven climatic variables, namely:
As demonstrated in Figure 1 (for January), there is likely to be little change in outdoor comfort levels in late
fall and winter (November-February), with Florida remaining the most desirable location for outdoor
activities from a climatic perspective. Early spring (March) is likely to see some improvement in outdoor
comfort levels across the entire nation, while summer (June-September) is likely to see a deterioration in
almost all areas other than Alaska and parts of the north-west. This probable decline in outdoor comfort
levels is demonstrated by the decline in orange and yellow shaded areas, and northwards shift of blue and
green areas, between Figures 2A and 2B (for July). In late spring (April, May) and mid-fall (October), there
is likely to be improvement in outdoor comfort levels in the northern states, but deterioration in the south.
Figure 3 demonstrates the range of potential impacts on tourism and recreation comfort levels across four
representative urban areas, Anchorage, Boston, San Francisco and Miami.
In Anchorage, climate change may eventually lead to a considerable increase in outdoor comfort in the
summer season (May-August), though the index remains below 70 in all but one of the cases (July of the
2080s). Conditions appear likely to remain unchanged throughout the remainder of the year, suggesting a
minimal impact on comfort levels throughout that period;
In Boston, comfort levels appear likely to decline (considerably by the 2050s) in July and August, though
increase somewhat in May and October;
San Francisco appears likely to experience an increase in comfort levels year round, other than a possible
decline in August in the 2080s. Overall, the analysis suggests that this city will become an even more
attractive destination for outdoor recreation activities than it already is;
Miami appears likely to experience a decline in comfort levels in all months, though this decline is at a
minimum in winter (December and January). Overall, however, the pattern of attractiveness (highest
November-March, lowest June-September) remains unaltered.
Figure 3 TCI for Anchorage, Boston, San Francisco and Miami, 1970s-2080s
As suggested by Figures 1-3, the most pleasant climatic conditions in the West, Midwest and Northeast have
historically occurred in the summer months. In the South, spring and fall have traditionally been the most
pleasant seasons (winter in the case of Florida), due to the excessively hot summers often experienced. As a
result of climate change, these patterns are likely to shift gradually to the north, however. The summer
season in the mid-Atlantic, in New England, and eventually even on the Pacific coast, will gradually become
too hot for comfort. By the 2050s Anchorage may, from a climate perspective, be a more pleasant place to
spend the month of August than Boston.
Conclusion
(i) maximum daily temperature; (ii) mean daily temperature; (iii) minimum daily relative humidity; (iv) daily
relative humidity; (v) precipitation; (vi) daily duration of sunshine; and, (vii) wind speed.
These seven variables were then weighted by Mieczkowski according to their relative influence on tourist
and recreationalist well-being to form the final index:
TCI = 4CID + CIA + 2R + 2S + W
Where: CID = daytime comfort index (composed of maximum daily temperature and minimum daily relative
humidity); CIA = daily comfort index (composed of mean daily temperature and daily relative humidity);
R = precipitation; S = daily sunshine; and, W = wind speed.
The temporal and spatial shifts in optimal climatic comfort levels for outdoor recreation suggested by the
analyses presented here have significant implications for the planning, provision and management of outdoor
recreation (OR) opportunities. To most effectively serve their customers, it is vital that OR planners and
managers recognize the potential for such shifts, and begin to incorporate them into their long-term planning
and development activities. A proactive approach to climate change adaptation will help minimize the cost of
necessary measures, as well as maximize the ability to capitalize on positive changes in outdoor comfort
levels. Future research should focus on finer scaled analyses – both spatially and temporally – as well as on
the implications of climate change for specific OR sectors, e.g., skiing or golf.
References
Each variable takes on an optimal rating of 5.0, and Mieczkowski suggested the classification scheme
outlined below be used to distinguish the suitability of a location’s climate for recreation and tourism based
on its overall TCI score:
Score
Comfort level
Score
Comfort level
90 – 100
80 – 89
70 – 79
60 – 69
50 – 59
Ideal
Excellent
Very good
Good
Acceptable
40 – 49
30 – 39
20 – 29
10 – 19
Below 9
Marginal
Unfavourable
Very unfavourable
Extremely unfavourable
Impossible
IPCC (2001) Climate Change 2001: The Scientific Basis. Contribution of Working Group I to the Third
Assessment Report of the Intergovernmental Panel on Climate Change, Houghton, J.T., Ding, Y.,
Griggs, D.J., Noguer, M., van der Linden, P.J., Dai, X., Maskell, K., & Johnson C.A. (eds.),
Cambridge University Press, Cambridge, United Kingdom and New York, NY, United States of
America.
Jones, P.D., New, M., Parker, D.E., Martin, S., & Rigor, I.G. (1999) ‘Surface air temperature and its
changes over the past 150 years,’ Reviews of Geophysics, 37, 173-199.
Jones, P.D., & Moberg, A. (2003) ‘Hemispheric and large-scale surface air temperature variations: An
extensive revision and an update to 2001,’ Journal of Climate, 16, 206-223.
Mieczkowski, Z. (1985) ‘The tourism climatic index: A method of evaluating world climates for tourism,’
Canadian Geographer, 29(3), 220-233.
The Authors: Sarah Nicholls is an Assistant Professor in the Departments of Community, Agriculture, Recreation & Resource Studies, and Geography, at Michigan State University. Bas Amelung is a Research Associate in the International Centre for Integrative Studies at the
University of Maastricht, in the Netherlands. David Viner is a Senior Research Associate in the Climatic Research Unit (CRU) at the University of East Anglia, UK. The work presented was completed during visits to CRU by Nicholls (January-February 2005, funded by an ESRCSSRC Visiting Collaborative Fellowship) and Amelung (August 2003, funded by the Center for Integrated Study of the Human Dimensions of Global Change ).