Statistics for Spatial Data.

Cause, conseguenze e strategie di mitigazione Proponiamo il primo di una serie di articoli in cui affronteremo l’attuale problema dei mutamenti climatici. Presentiamo il documento redatto, votato e pubblicato dall’Ipcc - Comitato intergovernativo sui cambiamenti climatici - che illustra la sintesi delle ricerche svolte su questo tema rilevante.

/pdf/climate-change-2007-the-physical-science-basis-1x93ttz9jt.pdf

Climate Change 2007: The Physical Science Basis.

The purpose of this paper is to provide a comprehensive presentation and interpretation of the Ensemble Kalman Filter (EnKF) and its numerical implementation. The EnKF has a large user group, and numerous publications have discussed applications and theoretical aspects of it. This paper reviews the important results from these studies and also presents new ideas and alternative interpretations which further explain the success of the EnKF. In addition to providing the theoretical framework needed for using the EnKF, there is also a focus on the algorithmic formulation and optimal numerical implementation. A program listing is given for some of the key subroutines. The paper also touches upon specific issues such as the use of nonlinear measurements, in situ profiles of temperature and salinity, and data which are available with high frequency in time. An ensemble based optimal interpolation (EnOI) scheme is presented as a cost-effective approach which may serve as an alternative to the EnKF in some applications. A fairly extensive discussion is devoted to the use of time correlated model errors and the estimation of model bias.

The Ensemble Kalman Filter: Theoretical formulation and practical implementation

http://lrc.geo.umn.edu/qpminor/May13%20Blaauw_inpress_QG.pdf

Methods and code for 'classical' age-modelling of radiocarbon sequences.

Understanding and quantifying the global methane (CH4) budget is important for assessing realistic pathways to mitigate climate change. Atmospheric emissions and concentrations of CH4 continue to increase, making CH4 the second most important human-influenced greenhouse gas in terms of climate forcing, after carbon dioxide (CO2). The relative importance of CH4 compared to CO2 depends on its shorter atmospheric lifetime, stronger warming potential, and variations in atmospheric growth rate over the past decade, the causes of which are still debated. Two major challenges in reducing uncertainties in the atmospheric growth rate arise from the variety of geographically overlapping CH4 sources and from the destruction of CH4 by short-lived hydroxyl radicals (OH). To address these challenges, we have established a consortium of multidisciplinary scientists under the umbrella of the Global Carbon Project to synthesize and stimulate new research aimed at improving and regularly updating the global methane budget. Following Saunois et al. (2016), we present here the second version of the living review paper dedicated to the decadal methane budget, integrating results of top-down studies (atmospheric observations within an atmospheric inverse-modelling framework) and bottom-up estimates (including process-based models for estimating land surface emissions and atmospheric chemistry, inventories of anthropogenic emissions, and data-driven extrapolations).

For the 2008–2017 decade, global methane emissions are estimated by atmospheric inversions (a top-down approach) to be 576 Tg CH4 yr−1 (range 550–594, corresponding to the minimum and maximum estimates of the model ensemble). Of this total, 359 Tg CH4 yr−1 or ∼ 60 % is attributed to anthropogenic sources, that is emissions caused by direct human activity (i.e. anthropogenic emissions; range 336–376 Tg CH4 yr−1 or 50 %–65 %). The mean annual total emission for the new decade (2008–2017) is 29 Tg CH4 yr−1 larger than our estimate for the previous decade (2000–2009), and 24 Tg CH4 yr−1 larger than the one reported in the previous budget for 2003–2012 (Saunois et al., 2016). Since 2012, global CH4 emissions have been tracking the warmest scenarios assessed by the Intergovernmental Panel on Climate Change. Bottom-up methods suggest almost 30 % larger global emissions (737 Tg CH4 yr−1, range 594–881) than top-down inversion methods. Indeed, bottom-up estimates for natural sources such as natural wetlands, other inland water systems, and geological sources are higher than top-down estimates. The atmospheric constraints on the top-down budget suggest that at least some of these bottom-up emissions are overestimated. The latitudinal distribution of atmospheric observation-based emissions indicates a predominance of tropical emissions (∼ 65 % of the global budget, < 30∘ N) compared to mid-latitudes (∼ 30 %, 30–60∘ N) and high northern latitudes (∼ 4 %, 60–90∘ N). The most important source of uncertainty in the methane budget is attributable to natural emissions, especially those from wetlands and other inland waters.

Some of our global source estimates are smaller than those in previously published budgets (Saunois et al., 2016; Kirschke et al., 2013). In particular wetland emissions are about 35 Tg CH4 yr−1 lower due to improved partition wetlands and other inland waters. Emissions from geological sources and wild animals are also found to be smaller by 7 Tg CH4 yr−1 by 8 Tg CH4 yr−1, respectively. However, the overall discrepancy between bottom-up and top-down estimates has been reduced by only 5 % compared to Saunois et al. (2016), due to a higher estimate of emissions from inland waters, highlighting the need for more detailed research on emissions factors. Priorities for improving the methane budget include (i) a global, high-resolution map of water-saturated soils and inundated areas emitting methane based on a robust classification of different types of emitting habitats; (ii) further development of process-based models for inland-water emissions; (iii) intensification of methane observations at local scales (e.g., FLUXNET-CH4 measurements) and urban-scale monitoring to constrain bottom-up land surface models, and at regional scales (surface networks and satellites) to constrain atmospheric inversions; (iv) improvements of transport models and the representation of photochemical sinks in top-down inversions; and (v) development of a 3D variational inversion system using isotopic and/or co-emitted species such as ethane to improve source partitioning.

/pdf/the-global-methane-budget-2000-2017-mbxchwmkf5.pdf

The global methane budget 2000–2017

. The continuous in situ measurement of δ18O in atmospheric CO2 opens a new door to differentiating between CO2 source and sink components with high temporal resolution. Continuous 13C–CO2 measurement systems have already been commercially available for some time, but until now, only few instruments have been able to provide a continuous measurement of the oxygen isotope ratio in CO2. Besides precise 13C/12C observations, the Fourier transform infrared (FTIR) spectrometer is also able to measure the 18O / 16O ratio in CO2, but the precision and accuracy of the measurements have not yet been evaluated. Here we present a first analysis of δ18O-CO2 (and δ13C-CO2) measurements with the FTIR analyser in Heidelberg. We used Allan deviation to determine the repeatability of δ18O-CO2 measurements and found that it decreases from 0.25‰ for 10 min averages to about 0.1‰ after 2 h and remains at that value up to 24 h. We evaluated the measurement precision over a 10-month period (intermediate measurement precision) using daily working gas measurements and found that our spectrometer measured δ18O-CO2 to better than 0.3‰ at a temporal resolution of less than 10 min. The compatibility of our FTIR-spectrometric measurements to isotope-ratio mass-spectrometric (IRMS) measurements was determined by comparing FTIR measurements of cylinder gases and ambient air with IRMS measurements of flask samples, filled with gases of the same cylinders or collected from the same ambient air intake. Two-sample t tests revealed that, at the 0.01 significance level, the FTIR and the IRMS measurements do not differ significantly from each other and are thus compatible. We describe two weekly episodes of ambient air measurements, one in winter and one in summer, and discuss what potential insights and new challenges combined highly resolved CO2, δ13C-CO2 and δ18O-CO2 records may provide in terms of better understanding regional scale continental carbon exchange processes.

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First continuous measurements of δ 18 O-CO 2 in air with a Fourier transform infrared spectrometer

. In situ CO2 and CO measurements from five
Integrated Carbon Observation System (ICOS) atmosphere stations have been
analysed together with footprint model runs from the regional Stochastic Time-Inverted Lagrangian Transport (STILT) model to develop a dedicated strategy for flask sampling with an
automated sampler. Flask sampling in ICOS has three different purposes, namely (1) to provide an independent quality control for in situ observations, (2) to provide
representative information on atmospheric components currently not monitored in situ at the stations, and (3) to collect samples for 14CO2 analysis
that are significantly influenced by fossil fuel CO2 ( ffCO2 )
emission areas. Based on the existing data and experimental results obtained
at the Heidelberg pilot station with a prototype flask sampler, we suggest
that single flask samples are collected regularly every third day around
noon or in the afternoon from the highest level of a tower station. Air samples shall
be collected over 1 h, with equal temporal weighting, to obtain a true
hourly mean. At all stations studied, more than 50 % of flasks collected around midday will likely be sampled during low ambient
variability ( parts per million (ppm) standard deviation of 1 min values).
Based on a first application at the Hohenpeisenberg ICOS site, such
flask data are principally suitable for detecting CO2 concentration biases
larger than 0.1 ppm with a 1 σ confidence level between flask and in situ observations from only five flask comparisons. In order to have a
maximum chance to also sample ffCO2 emission areas, additional flasks
are collected on all other days in the afternoon. To check if the
 ffCO2 component will indeed be large in these samples, we use the continuous in situ CO observations. The CO deviation from an estimated background value
is determined the day after each flask sampling, and depending on this
offset, an automated decision is made as to whether a flask shall be retained for
 14CO2 analysis. It turned out that, based on existing data,
 ffCO2 events of more than 4–5 ppm that would allow ffCO2 estimates
with an uncertainty below 30 % were very rare at all stations
studied, particularly in summer (only zero to five events per month from May to
August). During the other seasons, events could be collected more
frequently. The strategy developed in this project is currently being
implemented at the ICOS stations.

/pdf/a-dedicated-flask-sampling-strategy-developed-for-integrated-3o5ixh3ha4.pdf

A dedicated flask sampling strategy developed for Integrated Carbon Observation System (ICOS) stations based on CO2 and CO measurements and Stochastic Time-Inverted Lagrangian Transport (STILT) footprint modelling

 Atmospheric Δ14CO2 measurements are a
well-established tool to estimate the regional fossil-fuel-derived
 CO2 component However, emissions from nuclear facilities can
significantly alter the regional Δ14CO2 level In order to
accurately quantify the signal originating from fossil CO2 emissions, a
correction term for anthropogenic 14CO2 sources has to be
determined In this study, the HYSPLIT atmospheric dispersion model has been
applied to calculate this correction for the long-term Δ14 CO2 monitoring site in Heidelberg Wind fields with a spatial
resolution of 25 ∘ ×  25 ∘ ,
1 ∘ ×  1 ∘ , and 05 ∘ ×  05 ∘ show systematic deviations, with coarser
resolved wind fields leading to higher mean values for the correction The
finally applied mean Δ14CO2 correction for the period from
1986–2014 is 23 ‰ with a standard deviation of 21 ‰
and maximum values up to 152 ‰
These results are based on the 05 ∘ ×  05 ∘ wind field
simulations in years when these fields were available (2009, 2011–2014), and
for the other years they are based on 25 ∘ ×  25 ∘ wind
field simulations, corrected with a factor of 043 After operations at the
Philippsburg boiling water reactor ceased in 2011, the monthly nuclear
correction terms decreased to less than 2 ‰, with a
mean value of 044  ±  032 ‰ from 2012 to 2014

/pdf/the-influence-of-14-co-2-releases-from-regional-nuclear-4v3x4qeeij.pdf

Samuel Hammer

Papers

First continuous measurements of δ 18 O-CO 2 in air with a Fourier transform infrared spectrometer

A dedicated flask sampling strategy developed for Integrated Carbon Observation System (ICOS) stations based on CO2 and CO measurements and Stochastic Time-Inverted Lagrangian Transport (STILT) footprint modelling

The influence of 14 CO 2 releases from regional nuclear facilities at the Heidelberg 14 CO 2 sampling site (1986–2014)

Modelling the global and regional scale variability in atmospheric H2 with the two-way nested TM5 model

ICOS and global initiatives working towards policy-relevant, coordinated carbon and greenhouse gas observations