Climate change will have impacts on many different sectors of society, but a systematic method to quantify human well-being and livelihoods across sectors is so far unavailable. This paper presents the AHEAD approach, which allows for relating impacts of climate change to 16 dimensions of livelihoods and well-being. Using the example of changes in water availability, the results show how climate change impacts AHEAD. The approach also provides a tool to frame uncertainties from climate models.

Climate sensitivity can be quantified using measured changes in temperature and forcings. This approach requires disentangling natural and anthropogenic influences on global climate. We focused on the role of the Atlantic Multidecadal Oscillation (AMO) in this and show how different AMO characterizations influence the anthropogenic temperature trends (we found they were in between previously published values) and transient climate sensitivity, which we found to be 1.6 (1.0-3.3)°C.

Recent studies have identified an approximately proportional relationship between global warming and cumulative carbon emissions. This relationship – referred to as the transient climate response to cumulative carbon emissions (TCRE) – is useful for climate policy applications. We show that the TCRE is constant for cumulative emissions lower than ~1500GtC but declines for higher cumulative emissions. We also find the TCRE to decrease with increasing emission rate.

This paper presents the CMIP5 model predictions on the seasonal characteristics of global carbon cycle. We show a model consensus that the amplitude of this seasonal cycle will increase in the future under the RCP8.5 emission scenario. This is mostly due to enhanced ecosystem productivity in high latitude regions. While the models' ensemble CO2 amplitude increase is close to observation, our results suggest the underlying mechanisms may not be realistic.

We investigate the temporal characteristics of partitioned evaporation on land, and we present STEAM (Simple Terrestrial Evaporation to Atmosphere Model) -- a hydrological land-surface model developed to provide inputs to moisture tracking. The terrestrial residence timescale of transpiration (days to months) has larger inter-seasonal variation and is substantially longer than that of interception (hours). This can cause differences in moisture recycling, which is investigated more in Part 2.

Phosphate rock is a finite resource required for fertilizer production. Following a debate over the PR depletion timeline, global PR reserves were recently increased 4-fold based mainly on a restatement of Moroccan reserves. We review whether this restatement is methodologically compatible with resource terminology used in major resource classifications, whether resource classification nomenclature is sufficiently understood in the literature, and whether the recent restatements are reliable.