Transparency and reproducibility are key ingredients of good science, and require that data and methods, including computer code, be made available. In this collection of opinion pieces, we highlight some of the chances and challenges in opening code and data to the scrutiny of the scientific community and the world at large.

The countdown is on to reach a legally binding agreement between all nations on actions to mitigate climate change. In 2011, the United Nations Climate Change Conference agreed that such a deal will be in place by 2015, and implemented by 2020. In this joint web Focus, timed to coincide with the New York Climate Summit, Nature GeoscienceandNature Climate Changepresent a series of overview articles and opinion pieces that take stock of emissions and climate change uncertainties and discuss potential ways forward.

The countdown is on to reach a legally binding agreement between all nations on actions to mitigate climate change. In 2011, the United Nations Climate Change Conference agreed that such a deal will be in place by 2015, and implemented by 2020. In this joint web Focus, timed to coincide with the New York Climate Summit, Nature GeoscienceandNature Climate Changepresent a series of overview articles and opinion pieces that take stock of emissions and climate change uncertainties and discuss potential ways forward.

The long-held notion of a bone-dry Moon was challenged in 2008, with the detection of water in some of the Apollo samples. Since then, lunar scientists have sought to understand how much water is in the Moon, where it is, and where it comes from. In this web focus, we present an overview article, research papers and opinion pieces that evaluate the evidence for water in the lunar interior and on the lunar surface and discuss its origin — whether it was added by cometary impacts, implanted by the solar wind, or indigenous to a Moon that may not, in fact, have formed dry.

If food production is to keep pace with the demands of an ever-expanding global population, agricultural systems must be modified to cope with the rising temperatures and increased prevalence of droughts, floods and other extreme weather events that are projected to ensue. A series of opinion pieces in this issue explore some of the ways in which productivity can be improved and food security safeguarded, be it through the direct involvement of those that work on the land, partnerships between remote investors and local land owners, or treatments tailored to the agricultural system in hand.

Today, life on Earth depends on the availability of free oxygen, whether in the atmosphere, oceans, or aquatic systems. However, oxygen concentrations were low and variable for most of the first four billion years of Earth’s history. In this web focus we bring together a collection of research and review articles and opinion pieces tracing the origins of oxygenic photosynthesis and the factors that allowed oxygen to accumulate in the oceans and atmosphere.

From the industrial revolution onwards, greenhouse gas emissions resulting from human activities such as the burning of fossil fuel and changes in land use have caused the planet to warm. However, since 1998 – a year of record warmth – the rate of warming has been lower than in the late twentieth century. In this joint web focus, Nature Climate ChangeandNature Geosciencepresent original research and opinion pieces that discuss the causes of the slowdown in surface warming and examine how the science has been communicated by researchers and the media.

From the industrial revolution onwards, greenhouse gas emissions resulting from human activities such as the burning of fossil fuel and changes in land use have caused the planet to warm. However, since 1998 — a year of record warmth — the rate of warming has been lower than in the late twentieth century. In this joint web focus, Nature Climate ChangeandNature Geosciencepresent original research and opinion pieces that discuss the causes of the slowdown in surface warming and examine how the science has been communicated by researchers and the media.

Recent research has highlighted problems with our present explanation for how the Moon formed in the 'giant impact' of a large solar system body with the early Earth. In September 2013, London saw the latest in a series of landmark meetings debating theories of the Moon's origin, following others in 1984 (Kona, Hawaii) and 1998 (Monterey, California). These issues are now explored in a NatureCommentary,NatureNews & Views Forum andNature GeoscienceNews & Views article. We also present below a selection of recentNatureandNature Geosciencecontent related to the age, composition and origin of the Moon.

Recent research has highlighted problems with our present explanation for how the Moon formed in the giant impact of a large solar system body with the early Earth. In September 2013, London saw the latest in a series of landmark meetings debating theories of the Moon's origin, following others in 1984 (Kona, Hawaii) and 1998 (Monterey, California). These issues are now explored in a NatureCommentary,NatureNews & Views forum andNature GeoscienceNews & Views article. We also present a selection of recentNatureandNature Geosciencecontent related to the age, composition and origin of the Moon.

The demand for metals and other natural resources is surging and, in some instances, demand has already outstripped supply. Discovery of new deposits or the exploitation of known lower-grade ore deposits could offer solutions, but their implementation is not always straightforward, given political constraints and the complexities of international trade. This focus issue brings together a collection of review articles and opinion pieces that highlight the emerging science of the processes responsible for the formation of economic-grade ore deposits, and discuss the societal conditions and implications of their exploitation.

Microbes regulate the cycling of elements throughout the global ocean, from the icy surface waters that circulate at high latitudes, to the deep and surprisingly diverse vents that dot the continental seafloor. Human activities are starting to modify the way in which microbes mediate these cycles, at least in the relatively well-characterised waters of the upper ocean. The deeper layers of the ocean are probably less affected, at least at present, and are definitely less well explored. However, technological advances are starting to shed light on the cycling of elements at depth, revealing microbial systems that are quite different from those at the surface. In this Nature GeoscienceInsight we highlight some of the most intriguing advances in the microbial biogeochemistry of the oceans, a field that is very much in flux.