Causes of change in Northern Hemisphere winter meridional winds and regional hydroclimate

A critical aspect of human-induced climate change is how it will affect precipitation around the world. Broadly speaking, warming increases atmospheric moisture holding capacity, intensifies moisture transports and makes sub-tropical dry regions drier and tropical and mid-to-high-latitude wet regions wetter. Extra-tropical precipitation patterns vary strongly with longitude, however, owing to the control exerted by the storm tracks and quasi-stationary highs and lows or stationary waves. Regional precipitation change will, therefore, also depend on how these aspects of the circulation respond. Current climate models robustly predict a change in the Northern Hemisphere (NH) winter stationary wave field that brings wetting southerlies to the west coast of North America, and drying northerlies to interior southwest North America and the eastern Mediterranean. Here we show that this change in the meridional wind field is caused by strengthened zonal mean westerlies in the sub-tropical upper troposphere, which alters the character of intermediate-scale stationary waves. Thus, a robust and easily understood model response to global warming is the prime cause of these regional wind changes. However, the majority of models probably overestimate the magnitude of this response because of biases in their climatological representation of the relevant waves, suggesting that winter season wetting of the North American west coast will be notably less than projected by the multi-model mean

Promoting Climate-Smart Agriculture Through Water and Nutrient Interactions Options in Semi-arid West Africa: A Review of Evidence and Empirical Analysis

In this paper, we analysed the ability of a range of existing technologies and practices and explored how their outcomes are linked to climate change adaptation and mitigation in West Africa. The rapid population growth alongside poor land use and management resulted in soil and water erosion, desertification, and salinization, creating a spiralling decline in the productivity of the land for food and other ecosystem services. Climate change brings additional threats arising from stresses and shocks caused by higher temperatures and lack of rainfall. Thus, farmers need to utilize agricultural strategies that sustainably increase productivity, resilience, while reducing GHGs emissions where possible. In order to implement such climate-smart agriculture options in semi-arid West Africa, water has to be available for crop nutrient uptake in the right amounts and at the right time, as water stress during plant growth results in major yield reductions for most crops. Also, farmers need to use more inorganic fertiliser, while striking the right balance between managing soil organic matter, fertility and moisture content and the use of fertilisers. The most successful systems are those that provide water, nutrients and a supportive soil structure in a synergistic manner. Indeed, we found that technologies such as zaï, half-moons, stone bunds combined with application of organic/inorganic sources of nutrients, are promising climate-smart agriculture practices that could be widely used by smallholder farmers to maintain food production and secure farmers’ livelihoods, while possibly protecting the environment. These successful examples can serve as inspiration for future policies and investments that pursue food security goals at all scales