Energy efficiency and greenhouse gas emissions are closely linked. This paper reviews agricultural options to reduce energy intensities and their impacts, discusses important accounting issues related to system boundaries, land scarcity, and measurement units and compares agricultural energy intensities and improvement potentials on an international level.

This study analyzes the role of energy intensity improvement in the short term (to the year 2020) and midterm (to the year 2050) in the context of long-term greenhouse gases (GHG) stabilization scenarios. The data come from the latest Emissions Scenarios Database and were reviewed in the Fourth Assessment Report (AR4) by the Intergovernmental Panel on Climate Change.

The world's two largest emitters of greenhouse gases, China and the US, are showing positive signs of greening.

In their Commentary 'Dangerous assumptions' (Nature 452, 531

Pielke et al. correctly point out in their Commentary 'Dangerous assumptions' (Nature 452, 531

How big is the energy challenge of climate change? The technological advances needed to stabilize carbon dioxide emissions may be greater than we think, argue Roger Pielke Jr, Tom Wigley and Christopher Green.

The Intergovernmental Panel on Climate Change (IPCC) has grossly underestimated the challenges of reducing and stabilizing greenhousegas emissions, according to an influential group of climate-policy experts.