Climate Change refers to a statistically significant variation in either the mean state of the climate or in its variability which may be due to natural processes or external forcing, or to persistent anthropogenic changes in the composition of the atmosphere or in land use.

Causes of Climate change

A. External causes

1.  Solar activity

The energy output of the sun is not constant, it varies over time and it has an impact on our climate.

2.  Earth’s orbit

Earth’s orientation changes with time and over about 41 000 years it moves from 22.1 degrees to 24.5 degrees and back again. When the angle increases the summers become warmer and the winters become colder.

 3. Meteorites

B. Internal causes

1.  Natural

a. Plate tectonic and Volcanic eruption

For example, mountains formed in Himalayas. Large mountain chains can influence the circulation of air around the globe, and consequently influence the climate. Volcanos cause temperature change.

2.  Anthropogenic

The actual problem resulting in increased climate change.

a. Emissions of greenhouse gases

b. Particles/clouds

c. Land change

What are the impacts of climate change?

1. On agroecosystem

1.  Reduce crop duration.

2. Increase crop respiration rates.

3.    3.  Alter photosynthate partitioning to economic products.
4.       Affect the survival and distribution of pest populations.
5.       Hasten nutrient mineralization in soils.
6.       Decrease fertilizer-use efficiencies.
7.       Increase evapo-transpiration rate.
8.       Insect-pests will become more abundant through a number of inter- related processes, including range extensions and phenological changes, as well as increased rates of population development, growth, migration and over-wintering.
9.       An increase in atmospheric level will have a fertilization effect on crops with C3 photosynthetic pathway and thus will promote their growth and productivity.

2. On crops ( based on the researches being conducted in Nepal)

1.       1. Projected increase in carbon dioxide in the atmosphere is beneficial to crops: Increase to 550 ppm increases yields of crops such as wheat and rice by 10-20%
2.       Rice yields estimated to decrease by 10% for every 1°C temperature increase
3.       Productivity of most crops to remain unaffected/ marginally decrease by 2020 but decrease by 10-40% by 2100 (Aggarwal, 2009)
4.       Horticultural crops are more susceptible
5.       Positive found in case of Phaselous bean, onion and sweetcorn
6.       Initial National Communication, 2004 states that with the increase of temperature beyond 4 degree Celsius, the yield of Terai rice is projected to decrease.
7.       The yield of wheat is projected to fall down with the rise in temperature in Terai.
8.       It affects less in the hills than in Terai but increases production of maize in mountain areas.

3. On soil process

1.      1.  Disturbs water balance
2.       Flooding and run off
3.       Drought

4. On insects, pathogen and weeds

1.       1. Greater numbers, increased insecticide resistance
2.       Geographic ranges increases or decreases
3.       Host-pathogen response changes
4.       Cultural control measures may be less reliable
5.       Increased vigor of weeds and herbicide resistance
6.       Extreme events can spread

5. On livestock

1.       Heat stress can increase vulnerability to disease, reduce fertility, and reduce milk production.
2.       Drought may threaten pasture and feed supplies.
3.       Climate change may increase the prevalence of parasites and diseases that affect livestock.
4.       High temperature cause lignification.

6. On Biodiversity

1.     1.   With 4.5 c increase , major extinction
2.       Reduction of 15-37 % of plant and animals will extinct between 2050
3.       About 30 % plant and animal vulnerable if temp increases 1.5- 2.5 degree C.

What can we do now?

1.       Act now

a.       a. Building Adaptive Capacity
b.       Reducing Vulnerability
c.       Stringent National adaptation Plans

2.       Act together

a.       Reduce emissions

b.       Low use of fossil fuels

c.       Abide by global rules and regulations

3.       Act differently

a.       Climate Smart agriculture

b.       Carbon free technology

c.       Renewable energy

Source: IPCC