Signal amplification by reversible exchange (SABRE) turns typically weak magnetic resonance responses into strong signals making previously impractical measurements possible. This technique has ...gained significant popularity because of its speed and simplicity. This Minireview tracks the development of SABRE from the initial hyperpolarization of pyridine in 2009 to the point in which 50 % 1H polarization levels have been achieved in a di‐deuterio‐nicotinate, a key step in the pathway to potential clinical use. Simple routes to highly efficient 15N hyperpolarization and the creation of hyperpolarized long‐lived magnetic states are illustrated. To conclude, we describe how the recently reported SABRE‐RELAY approach offers a route for parahydrogen to hyperpolarize a much wider array of molecular scaffolds, such as amides, alcohols, carboxylic acids, and phosphates, than was previously thought possible. We predict that collectively these developments ensure that SABRE will significantly impact on both chemical analysis and the diagnosis of disease in the future.
SABRE‐rattling: Signal amplification by reversible exchange (SABRE) is a hyperpolarization technique that dramatically enhances magnetic resonance signals. This Minireview tracks its development since its discovery in 2009 and offers an outlook on its potential use for both analytic sciences and disease diagnosis.
Anthropogenic increases in atmospheric greenhouse gas
concentrations are the main driver of current and future climate change. The
integrated assessment community has quantified anthropogenic ...emissions for
the shared socio-economic pathway (SSP) scenarios, each of which represents
a different future socio-economic projection and political environment.
Here, we provide the greenhouse gas concentrations for these SSP scenarios
– using the reduced-complexity climate–carbon-cycle model MAGICC7.0. We
extend historical, observationally based concentration data with SSP
concentration projections from 2015 to 2500 for 43 greenhouse gases with monthly and latitudinal resolution. CO2 concentrations by 2100 range
from 393 to 1135 ppm for the lowest (SSP1-1.9) and highest (SSP5-8.5)
emission scenarios, respectively. We also provide the concentration
extensions beyond 2100 based on assumptions regarding the trajectories of fossil
fuels and land use change emissions, net negative emissions, and the
fraction of non-CO2 emissions. By 2150, CO2 concentrations in the
lowest emission scenario are approximately 350 ppm and approximately plateau
at that level until 2500, whereas the highest fossil-fuel-driven scenario
projects CO2 concentrations of 1737 ppm and reaches concentrations
beyond 2000 ppm by 2250. We estimate that the share of CO2 in the total
radiative forcing contribution of all considered 43 long-lived greenhouse
gases increases from 66 % for the present day to roughly 68 % to 85 % by
the time of maximum forcing in the 21st century. For this estimation,
we updated simple radiative forcing parameterizations that reflect the Oslo
Line-By-Line model results. In comparison to the representative concentration pathways (RCPs), the five main SSPs
(SSP1-1.9, SSP1-2.6, SSP2-4.5, SSP3-7.0, and SSP5-8.5) are more evenly spaced
and extend to lower 2100 radiative forcing and temperatures. Performing two
pairs of six-member historical ensembles with CESM1.2.2, we estimate the
effect on surface air temperatures of applying latitudinally and seasonally
resolved GHG concentrations. We find that the ensemble differences in the
March–April–May (MAM) season provide a regional warming in higher northern
latitudes of up to 0.4 K over the historical period, latitudinally averaged
of about 0.1 K, which we estimate to be comparable to the upper bound
(∼5 % level) of natural variability. In comparison to the
comparatively straight line of the last 2000 years, the greenhouse gas
concentrations since the onset of the industrial period and this studies'
projections over the next 100 to 500 years unequivocally depict a
“hockey-stick” upwards shape. The SSP concentration time series derived in
this study provide a harmonized set of input assumptions for long-term
climate science analysis; they also provide an indication of the wide set of
futures that societal developments and policy implementations can lead to –
ranging from multiple degrees of future warming on the one side to
approximately 1.5 ∘C warming on the other.
Iridium N-heterocyclic carbene (NHC) complexes catalyse the para-hydrogen-induced hyperpolarization process, Signal Amplification by Reversible Exchange (SABRE). This process transfers the latent ...magnetism of para-hydrogen into a substrate, without changing its chemical identity, to dramatically improve its nuclear magnetic resonance (NMR) detectability. By synthesizing and examining over 30 NHC containing complexes, here we rationalize the key characteristics of efficient SABRE catalysis prior to using appropriate catalyst-substrate combinations to quantify the substrate's NMR detectability. These optimizations deliver polarizations of 63% for
H nuclei in methyl 4,6-d
-nicotinate, 25% for
C nuclei in a
C
-diphenylpyridazine and 43% for the
N nucleus of pyridine-
N. These high detectability levels compare favourably with the 0.0005%
H value harnessed by a routine 1.5 T clinical MRI system. As signal strength scales with the square of the number of observations, these low cost innovations offer remarkable improvements in detectability threshold that offer routes to significantly reduce measurement time.
Atmospheric greenhouse gas (GHG) concentrations are at unprecedented, record-high levels compared to the last 800 000 years. Those elevated GHG concentrations warm the planet and – partially offset ...by net cooling effects by aerosols – are largely responsible for the observed warming over the past 150 years. An accurate representation of GHG concentrations is hence important to understand and model recent climate change. So far, community efforts to create composite datasets of GHG concentrations with seasonal and latitudinal information have focused on marine boundary layer conditions and recent trends since the 1980s. Here, we provide consolidated datasets of historical atmospheric concentrations (mole fractions) of 43 GHGs to be used in the Climate Model Intercomparison Project – Phase 6 (CMIP6) experiments. The presented datasets are based on AGAGE and NOAA networks, firn and ice core data, and archived air data, and a large set of published studies. In contrast to previous intercomparisons, the new datasets are latitudinally resolved and include seasonality. We focus on the period 1850–2014 for historical CMIP6 runs, but data are also provided for the last 2000 years. We provide consolidated datasets in various spatiotemporal resolutions for carbon dioxide (CO2), methane (CH4) and nitrous oxide (N2O), as well as 40 other GHGs, namely 17 ozone-depleting substances, 11 hydrofluorocarbons (HFCs), 9 perfluorocarbons (PFCs), sulfur hexafluoride (SF6), nitrogen trifluoride (NF3) and sulfuryl fluoride (SO2F2). In addition, we provide three equivalence species that aggregate concentrations of GHGs other than CO2, CH4 and N2O, weighted by their radiative forcing efficiencies. For the year 1850, which is used for pre-industrial control runs, we estimate annual global-mean surface concentrations of CO2 at 284.3 ppm, CH4 at 808.2 ppb and N2O at 273.0 ppb. The data are available at https://esgf-node.llnl.gov/search/input4mips/ and http://www.climatecollege.unimelb.edu.au/cmip6. While the minimum CMIP6 recommendation is to use the global- and annual-mean time series, modelling groups can also choose our monthly and latitudinally resolved concentrations, which imply a stronger radiative forcing in the Northern Hemisphere winter (due to the latitudinal gradient and seasonality).
Abstract
We use a globally consistent, time-resolved data set of CO
2
emission proxies to quantify urban CO
2
emissions in 91 cities. We decompose emission trends into contributions from changes in ...urban extent, population density and per capita emission. We find that urban CO
2
emissions are increasing everywhere but that the dominant contributors differ according to development level. A cluster analysis of factors shows that developing countries were dominated by cities with the rapid area and per capita CO
2
emissions increases. Cities in the developed world, by contrast, show slow area and per capita CO
2
emissions growth. China is an important intermediate case with rapid urban area growth combined with slower per capita CO
2
emissions growth. Urban per capita emissions are often lower than their national average for many developed countries, suggesting that urbanisation may reduce overall emissions. However, trends in per capita urban emissions are higher than their national equivalent almost everywhere, suggesting that urbanisation will become a more serious problem in the future. An important exception is China, whose per capita urban emissions are growing more slowly than the national value. We also see a negative correlation between trends in population density and per capita CO
2
emissions, highlighting a strong role for densification as a tool to reduce CO
2
emissions.
This paper presents the assimilation of solar-induced chlorophyll fluorescence (SIF) into a terrestrial biosphere model to estimate the gross uptake of carbon through photosynthesis (GPP). We use the ...BETHY-SCOPE model to simulate both GPP and SIF using a process-based formulation, going beyond a simple linear scaling between the two. We then use satellite SIF data from the Orbiting Carbon Observatory-2 (OCO-2) for 2015 in the data assimilation system to constrain model biophysical parameters and GPP. The assimilation results in considerable improvement in the fit between model and observed SIF, despite a limited capability to fit regions with large seasonal variability in SIF. The SIF assimilation increases global GPP by 31 % to 167±5 Pg C yr−1 and shows an improvement in the global distribution of productivity relative to independent estimates, but a large difference in magnitude. This change in global GPP is driven by an overall increase in photosynthetic light-use efficiency across almost all biomes and more minor, regionally distinct changes in APAR. This process-based data assimilation opens up new pathways to the effective utilization of satellite SIF data to improve our understanding of the global carbon cycle.
The climate-carbon cycle feedback is one of the most important climate-amplifying feedbacks of the Earth system, and is quantified as a function of carbon-concentration feedback parameter (β) and ...carbon-climate feedback parameter (γ). However, the global climate-amplifying effect from this feedback loop (determined by the gain factor, g) has not been quantified from observations. Here we apply a Fourier analysis-based carbon cycle feedback framework to the reconstructed records from 1850 to 2017 and 1000 to 1850 to estimate β and γ. We show that the β-feedback varies by less than 10% with an average of 3.22 ± 0.32 GtC ppm
for 1880-2017, whereas the γ-feedback increases from -33 ± 14 GtC K
on a decadal scale to -122 ± 60 GtC K
on a centennial scale for 1000-1850. Feedback analysis further reveals that the current amplification effect from the carbon cycle feedback is small (g is 0.01 ± 0.05), which is much lower than the estimates by the advanced Earth system models (g is 0.09 ± 0.04 for the historical period and is 0.15 ± 0.08 for the RCP8.5 scenario), implying that the future allowable CO
emissions could be 9 ± 7% more. Therefore, our findings provide new insights about the strength of climate-carbon cycle feedback and about observational constraints on models for projecting future climate.
Para
hydrogen is used to give efficient NMR detection of array of amines, amides, alcohols, carboxylates, carbonates, and phosphates.
Hyperpolarization turns weak nuclear magnetic resonance (NMR) and ...magnetic resonance imaging (MRI) responses into strong signals, so normally impractical measurements are possible. We use
para
hydrogen to rapidly hyperpolarize appropriate
1
H,
13
C,
15
N, and
31
P responses of analytes (such as NH
3
) and important amines (such as phenylethylamine), amides (such as acetamide, urea, and methacrylamide), alcohols spanning methanol through octanol and glucose, the sodium salts of carboxylic acids (such as acetic acid and pyruvic acid), sodium phosphate, disodium adenosine 5′-triphosphate, and sodium hydrogen carbonate. The associated signal gains are used to demonstrate that it is possible to collect informative single-shot NMR spectra of these analytes in seconds at the micromole level in a 9.4-T observation field. To achieve these wide-ranging signal gains, we first use the signal amplification by reversible exchange (SABRE) process to hyperpolarize an amine or ammonia and then use their exchangeable NH protons to relay polarization into the analyte without changing its identity. We found that the
1
H signal gains reach as high as 650-fold per proton, whereas for
13
C, the corresponding signal gains achieved in a
1
H-
13
C refocused insensitive nuclei enhanced by polarization transfer (INEPT) experiment exceed 570-fold and those in a direct-detected
13
C measurement exceed 400-fold. Thirty-one examples are described to demonstrate the applicability of this technique.
NASA's Orbiting Carbon Observatory will monitor the atmospheric concentrations of carbon dioxide (CO2) along the satellite subtrack over the sunlit hemisphere of the Earth for more than 2 years, ...starting in late 2008. This paper demonstrates the application of a variational Bayesian formalism to retrieve fluxes at high spatial and temporal resolution from the satellite retrievals. We use a randomization approach to estimate the posterior error statistics of the calculated fluxes. Given our prior information about the fluxes (with error standard deviations about 0.4 g C m−2 d−1 over ocean and 4 g C m−2 d−1 over vegetated areas) and our observation characteristics (with error standard deviations about 2 ppm), we show error reductions of up to about 40% at weekly scale for a grid point of the transport model. We simulate the impact of undetected biases by perturbing the observations and show that regional biases of a few tenths of a part per million in column‐averaged CO2 can bias the inverted yearly subcontinental fluxes by a few tenths of a gigaton of carbon, which is larger than the uncertainty on the anthropogenic carbon fluxes but smaller than that of natural fluxes over most vegetated areas.
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