California’s winters have become more drier in last 40 years. This has created problems in agricultural sectors as farmers depends on winter precipitation to irrigate their crops. If this situation will continue itself, it will impact millions of residents in California.
Researchers have made climate models to reproduce the effects of this trend, but they have faced trouble in reproducing California’s drying trends. Climate models could not project the long-term precipitation of winter dryness. Pacific Northwest National Laboratory researchers have tried to find out the reason of this result.
Ruby Leung, a scientist of PNNL has said that there are too much uncertainties in model and scientists are trying to find out if models are up for the task or not. There are challenges in modelling California such as long-term natural cycles affect its precipitation.
El Niño, La Niña and Interdecadal Pacific Oscillation influences the natural cycle. The natural cycle is also related to sea surface temperature patterns in the Pacific Ocean which impacts winter precipitation in California.
The team of scientists have found out natural cycles plays a big role in California’s precipitation projections. PNNL researchers found out natural cycles are responsible for nearly 70 percent of the uncertainty. Researchers have isolated the effects of the natural cycles to improve their new model. This model will help to understand how greenhouse gases affect climate.
Researchers now will run the new climate model 40–100 times and have noticed minor differences. All these differences indicated towards natural variability. Researchers derived at the conclusion that the whole uncertainty happens because of natural variability and model uncertainty.
The team of scientists have observed three ensemble simulations of three different climate models. They wanted to find out the sources of uncertainty in in California precipitation. They discovered 70 percent of the total uncertainty is caused by natural climate cycles and nearly 30 percent of the uncertainty happens due to human influence on climate.