Climate
change is primarily resulted from human-made activities resulting greenhouse
gases emissions and appearing as an increase in temperature and variability in
precipitation. According to NASA (2009), in total, average global
temperatures have increased by about 0.8°C (1.4°F) since 1880 (the year that
modern scientific instrumentation became available to monitor temperatures
precisely). World Meteorological Organization (2011) reported over the ten
years from 2001 to 2010, global average temperature is 0.46°C (0.83°F) above
the 1961-1990 average. This is the highest ever recorded for a 10-year period
since the beginning of instrumental climate records.
The
general trend in the Nepal record is quite similar to what has been found in
the global records although the magnitude of trends are different, suggesting
that the climate variations and changes in Nepal are impacted by global climate
change. Department of Hydrology and Meteorology (DHM) estimated from 1977 and
1994, the mean annual temperature to have increased by 0.06°C, and is projected
to increase by another 1.2°C by 2030, 1.7°C by 2050, and 3.0°C by 2100.
Analysis on rainfall data from station records all over Nepal show distinct
cyclic characteristics but does not
reveal any significant trends, as observed in temperature records.
Nepal
Engineering College under the research grant of International Development
Research Center, Canada, analyzed various attributes of rainfall and
temperature for seven stations of Kathmandu (Khumaltar, TIA, Godawari, Changu
Narayan, Naikap, Panipokhari and Sankhu) selected considering their proximity
to the peri-urban research sites of the ongoing project.
The
analysis of temperature record showed a clear decrease in number of days below
0°C and increase in number of hot days (> 30°C). The highest and the lowest
temperature of both daily Tmin (Minimum Temperature) and daily Tmax (Maximum
Temperature) showed an increase. This increase in temperature was the lowest
for the summer season and the strongest for fall and winter season. Tmin showed
an average increase of 0.04°C per year and Tmax showed on average an increase
of 0.05°C per year. More clearly, days and nights are both becoming warmer and
cool days and cool nights are becoming less frequent. Similarly summer days
with maximum temperatures above > 30°C are also increasing.
While
the changing trend of temperature can be expressed in terms of the mean over
time and the amount of variance about the mean, other meteorological variables
require more complicated statistical calculations. For instance, rainfall is
episodic. Considering WMO statement, in certain parts of the world especially
in the arid regions of the world precipitation are likely to decrease whereas
in the northern hemisphere the likelihood is that the precipitation would
increase. In Nepal, much of the annual rainfall falls in a short rainy
season. Analysis on rainfall data from station records all over Nepal does not
reveal any significant trends.
The
analysis of rainfall data from the above mentioned seven stations for
understanding the long term rainfall trend in Kathmandu showed no clear
increasing or decreasing trend in the number of days with rainfall. Similarly,
the trend for the total annual rainfall is not clearly defined. Upon
concentrating the analysis for monsoon period (June to September), no defined
trend could be drawn. An increase in the number of extreme rainfall events
(daily rainfall > 50mm) was found but concerning the intensity of rainfall
conducted for monsoon period in the study no recognizable pattern could be
concluded.
Uncontrolled urbanization and spreading infrastructure in
Kathmandu has contributed to reduced agriculture land, increasing congestion,
and environmental degradation associated with the poorly managed disposal of
solid and industrial wastes and other forms of pollution. An increased
frequency of extreme weather events attributed to anthropogenic climate change
can make the prospects for environmental sustainability and human security
disconcerting for example in unplanned land p. Increases in seasonal
temperatures are likely to affect agricultural production and yield. Higher temperatures have also been associated with an
increase in diarrhea, mild winters tend to increase rodent-borne diseases, and
can also increase dengue-fever transmitted by mosquitoes. Though the amount of
rainfall has not undergone decline, the water availability has been declining.
This decline is commonly perceived to be ensued from declining rainfall. Therefore,
strengthening the adoptive strategies in Kathmandu need activities
investigating knowledge, expertise and resources to raise awareness against the challenges
of pressure on resources and environment associated with urbanization, changing
climate and the compounded effects.