weather

par Sonja Vermeulen

La flambée des prix des denrées alimentaires est encore une fois parmi nous. Pour certains produits il y a un lien direct avec le climat. Aux Etats-Unis, les fortes chaleurs et la sécheresse ont pour la première fois dans l'histoire, envolés le prix du boisseau de maïs à plus de 8 $. Mais, les "vagues de chaleur" ont-elles des effets à long terme sur l'économie? Quelques réponses intéressantes apparaissent dans Temperature shocks and economic growth: evidence from the last half century, une étude économétrique de Melissa Dell, Benjamin Jones et Benjamin Olken, qui était disponible sous forme de Working Paper depuis la crise des prix des denrées alimentaires de 2008 et qui est désormais officiellement publiée.

L'étude analyse la relation entre les anomalies de températures et la performance économique dans 125 pays entre 1950 et 2003. En résumé, les pays riches ne montrent pas des impacts économiques significatifs liés aux chocs thermiques. Or dans les pays pauvres - qui ont également tendance à être chaud et agricole*- un écart-type de la température annuelle moyenne à la hausse réduit la croissance économique de 0,69 points de pourcentage. Cela signifie que les années qui sont 1C plus chaudes que la moyenne-se qui se produit environ une fois tous les 15 ans- sont associées à une réduction moyenne de la croissance économique de 1,3 points de pourcentage.

Sans surprise, l'impact de la température sur l'agriculture est majeur. Read more »

One of the challenges researchers face when communicating climate science is the distinction between climate and weather. The public and the media are often quick to conflate the two, resulting in confusion or worse, misinformation. Last year we covered the drought in the Horn of Africa, and highlighted the problems with attributing a single weather event to climate change.

The distinction between weather and climate is also important when communicating with farmers about the changes they can expect and plan for. In our work on Adaptation through Managing Climate Risk, we've been training farmers to read seasonal climate forecasts, to help them plan for longer term changes (as compared to weather forecasts which only predict a few days ahead).

This short video from the Norwegian TV program Siffer helps illustrate the difference between weather and climate simply and clearly.

The video was featured in a recent New York Times blog Can Better Communication of Climate Science Cut Climate Risks? by Andrew Revkin

Devastating reports coming from the Horn of Africa indicate that some places are experiencing the worst drought in 60 years. And while it may seem logical to blame the dry conditions on climate change, CCAFS theme leader Philip Thornton warns against attributing a single event to climate change. In a recent interview, he told IRIN Africa that there are challenges in projecting climate change impacts in East Africa:

”Some people think that East Africa is drying, and has dried over recent years; currently there is no hard, general evidence of this, and it is very difficult as yet to see where the statistical trends of rainfall in the region are heading, but these will of course become apparent in time.”

Good climate data (long‐term temporally homogeneous time series with good spatial coverage) is critical for assessing climate‐related risks, understanding climate change in a long-term context, understanding the impact of climate on different socioeconomic activities, and producing useful climate atlases. CCAFS partners are working on downscaling data to shorter time periods and smaller geographical areas, in order to make climate data more useful for agricultural decision-makers. The conventional source of climate data has been measurements at weather stations. However, the number and quality of weather stations in Africa, Latin America and other regions has been declining. Read more »