Climate Change Impact
Part 9: Example –Kyrgyzstan
Kyrgyzstan has a continental climate with cold winters and hot summers. Most of the rain falls in the summer months and temperatures are below freezing for most of the winter months. It is projected that storm rainfall will increase by up to 20% and that the duration of lying snow will decrease.
Kyrgyzstan is in central Asia and has severe winters with temperature below zero for many months, particularly in mountainous areas.
|Figure 1 Map of Kyrgyzstan showing project road|
Climate change can affect roads in many ways. The most obvious is storm rainfall; an increase in storm rainfall could require modification to current design for culverts and longitudinal drains. Other factors include daily temperature range, which could affect expansion joints, and maximum temperature, which could affect the choice of binding agent.
Once current values of these parameters have been determined then the extent to which they will change in the future can be assessed.
The observed climate data were downloaded from internet sites which process data facilitated by international organisations such as the World Meteorological Organisation.
Other documents related to climate change for Kyrgyzstan were downloaded. These included:
- UNFCCC Country Brief 2014: Kyrgyzstan
- Climate Profile of the Kyrgyz Republic
- The Kyrgyz Republic: Intended Nationally Determined Contribution
- The Kyrgyz Republic’s Second National Communication to the United Nations Framework Convention on Climate Change
These documents describe the potential change to the climate in general terms but were not specific enough for road design.
Kyrgyzstan has a continental climate with warm summer and cold winters.
The following chart shows the location of the climate stations which were used to determine current climate parameters. Only stations in the area of the project road are shown. The data were at a daily time step and included: precipitation, depth of snow, average daily temperature, daily maximum temperature and daily minimum temperature. Data were downloaded for the period 1950 to the present.
Figure 2 shows the location of sites with climate data. Sites with a solid diamond have precipitation, temperature and snow data. Sites with an open diamond only have precipitation data.
The chart also shows the area covered by the nearest climate model cell as an orange rectangle. It is convenient that the section of road of interest corresponds to one of the climate cells.
Rainfall is highest in the summer months. In winter, average monthly temperatures are often below zero. The road itself passes between two areas with higher elevations and maximum daily rainfall is lower than areas with higher land – around 20 mm per day.
To examine the performance of climate models, their simulation relative to past observed climate for the period 1970 to 1990 was examined. The four models chosen on this basis were:
- bcc-csm1-1: Beijing Climate Center Climate System Model (China)
- IPSL-CM5A-MR: The Institut Pierre Simon Laplace (France)
- CCSM4: The Community Climate System Model Version 4 (USA)
- NorESM1-M: Norwegian Earth System Model (Norway)
The conclusions relating to climate change and daily maximum rainfall were:
- The average percentage increase for the final 50 years of the present century is 7.3% for the RCP 8.5 projections and 5.5% for the RCP 6.0 projections.
- The projections of 5-day rainfall, more relevant for rivers which are crossed by the road showed a similar increase which could be translated in into increased flooding.
- Winter and summer temperatures have been rising in recent years. The rate of increase has been 3.3 °C per century, slightly lower than the projected 5.5 °C per century. This significance of these increases relate to icing in winter and the heat-resistance of the road surface in summer. There is no indication that the diurnal temperature range (important for expansion joints) will increase.
- On average, the depth of snow reaches 500 mm or even more in an average year.
· When a range of models was ranked on the projected increase between the present and the year 2100, the difference in projection between the upper and lower quartile was quite modest; of the order of 15%. This applied for both RCP 6.0 and RCP 8.5.
· When four selected models were compared their difference in projected values for the year 2100 was larger.
· In most cases the largest percentage increase in daily rainfall for any projection occurred not in the final year of this century but in an earlier year. At any time in the current century the increase in precipitation rarely exceeded 20%, apart from the few models with the highest rate of increase in precipitation. A further consideration following from this is that the maximum increase in rainfall could occur during the projected life of the road.
There are no specific projections related to snow depth. Figure 3 shows two alternative metrics. The first is ‘icing days’; these are days when the daily maximum temperature is below zero. The second is ‘frost days’; these are days when the daily minimum temperature is below zero. The decline in these two variables indicates two things. Firstly, that snow fall will be less frequent and secondly that it will lie for a shorter time.
Figure 3 Days with temperature below freezing for all or part of a day
The main conclusions are that there will be an increase in storm rainfall of up to 20% during the life of the road. The period with lying snow will reduce.