Climate Signal Detection Times and Constraints on Climate Benchmark Accuracy Requirements

Leroy, S. S.; Anderson, James G.; Ohring, George

doi:10.1175/2007jcli1946.1

Cited by 80 publications

(82 citation statements)

References 5 publications

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“…4 for all inspected RO variables. For different timescales the given (random) uncertainties scale as σ ( t/ t target ) 3/2 , where t is 7 yr and t target is the target time (Leroy et al, 2008) (e.g. σ = 3 m per 7 yr translates to an error of 2.5 m per 10 yr for a 10-yr time series).…”

Section: Mean Trends and Structural Uncertaintymentioning

confidence: 99%

Quantification of structural uncertainty in climate data records from GPS radio occultation

et al. 2013

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Global Positioning System (GPS) radio occultation (RO) has provided continuous observations of the Earth's atmosphere since 2001 with global coverage, all-weather capability, and high accuracy and vertical resolution in the upper troposphere and lower stratosphere (UTLS). Precise time measurements enable long-term stability but careful processing is needed. Here we provide climate-oriented atmospheric scientists with multicenter-based results on the long-term stability of RO climatological fields for trend studies. We quantify the structural uncertainty of atmospheric trends estimated from the RO record, which arises from current processing schemes of six international RO processing centers, DMI Copenhagen, EUM Darmstadt, GFZ Potsdam, JPL Pasadena, UCAR Boulder, and WEGC Graz. Monthly-mean zonal-mean fields of bending angle, refractivity, dry pressure, dry geopotential height, and dry temperature from the CHAMP mission are compared for September 2001 to September 2008. We find that structural uncertainty is lowest in the tropics and mid-latitudes (50° S to 50° N) from 8 km to 25 km for all inspected RO variables. In this region, the structural uncertainty in trends over 7 yr is <0.03% for bending angle, refractivity, and pressure, <3 m for geopotential height of pressure levels, and <0.06 K for temperature; low enough for detecting a climate change signal within about a decade. Larger structural uncertainty above about 25 km and at high latitudes is attributable to differences in the processing schemes, which undergo continuous improvements. Though current use of RO for reliable climate trend assessment is bound to 50° S to 50° N, our results show that quality, consistency, and reproducibility are favorable in the UTLS for the establishment of a climate benchmark record

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Section: Mean Trends and Structural Uncertaintymentioning

confidence: 99%

Quantification of structural uncertainty in climate data records from GPS radio occultation

et al. 2013

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“…instrument drift, sampling, seasonal variation, etc., in order to detect a trend in a climate parameter above a background of natural variability in a given time frame. Of course, there are fundamental limits to the accuracy of measuring climate trends, which can be set with reference to the perfect climate observing system following the methodology of Leroy et al [35]. Figure 4 presents the results of such an analysis for the CRF example using the proposed operational characteristics of TRUTHS and CLARREO.…”

Section: (Iii) Optimizing Uncertaintymentioning

confidence: 99%

Accurate radiometry from space: an essential tool for climate studies

Fox

Kaiser-Weiss

Schmutz

et al. 2011

Phil. Trans. R. Soc. A.

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The Earth's climate is undoubtedly changing; however, the time scale, consequences and causal attribution remain the subject of significant debate and uncertainty. Detection of subtle indicators from a background of natural variability requires measurements over a time base of decades. This places severe demands on the instrumentation used, requiring measurements of sufficient accuracy and sensitivity that can allow reliable judgements to be made decades apart. The International System of Units (SI) and the network of National Metrology Institutes were developed to address such requirements. However, ensuring and maintaining SI traceability of sufficient accuracy in instruments orbiting the Earth presents a significant new challenge to the metrology community. This paper highlights some key measurands and applications driving the uncertainty demand of the climate community in the solar reflective domain, e.g. solar irradiances and reflectances/radiances of the Earth. It discusses how meeting these uncertainties facilitate significant improvement in the forecasting abilities of climate models. After discussing the current state of the art, it describes a new satellite mission, called TRUTHS, which enables, for the first time, high-accuracy SI traceability to be established in orbit. The direct use of a 'primary standard' and replication of the terrestrial traceability chain extends the SI into space, in effect realizing a 'metrology laboratory in space'.

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“…detection time). As stated by Leroy et al (2008), it is obvious that the longer the time series, the easier it should be to distinguish a trend from natural variability (and measurement uncertainty), because shorter periods of record generally have small signal-to-noise (S / N) ratios (Allen et al, 1994). The strong timescale dependence of S / N ratios arises primarily because of the large decrease in noise amplitude as the period used for trend fitting increases (Santer et al, 2011).…”

Section: Discussionmentioning

confidence: 99%

“…The strong timescale dependence of S / N ratios arises primarily because of the large decrease in noise amplitude as the period used for trend fitting increases (Santer et al, 2011). Based on a hypothetical data set with certain statistical characteristics, Leroy et al (2008) determined the minimum detection time as about 33 yr for detecting a global warming signal of 0.2 K decade −1 . Similarly, assessing the trend consistency over a range of timescales (from 10 to 32 yr), Santer et al (2011) states that multi-decadal records are required for identifying the human effect on the climate variables (e.g.…”

Section: Discussionmentioning

confidence: 99%

Satellite-based analysis of recent trends in the ecohydrology of a semi-arid region

Gokmen

Vekerdy

Verhoef

et al. 2013

Hydrol. Earth Syst. Sci.

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Abstract. We present a regional framework for an integrated and spatiotemporally distributed assessment of human-induced trends in the hydrology and the associated ecological health of a semi-arid basin where both human activities (i.e. agriculture) and natural ecosystems are highly groundwater dependent. To achieve this, we analysed the recent trends (from year 2000 to 2010) in precipitation, evapotranspiration (actual and potential) and vegetation greenness (i.e. NDVI) using a combination of satellite and groundbased observations. The trend assessment was applied for the semi-arid Konya Basin (Turkey), one of the largest endorheic basins in the world.The results revealed a consistent increasing trend of both yearly evapotranspiration (totally 63 MCM yr −1 from croplands) and mean NDVI (about 0.004 NDVI yr −1 in irrigated croplands), especially concentrating in the plain part of the basin, while no significant trends were observed for the precipitation and potential evapotranspiration variables. On the contrary, a consistent decreasing trend of both yearly evapotranspiration (totally −2.1 MCM yr −1 ) and mean NDVI (−0.001 NDVI yr −1 ) was observed in the wetlands, which also cannot be explained by trends in precipitation and potential evapotranspiration. The emerging picture suggest that the greening trend of the vegetation and increasing of evapotranspiration in the plain are related to land cover changes (i.e. conversion into irrigated croplands) and to the intensification of the supplementary irrigation for agriculture, which in turn caused drying out of some wetlands and the natural vegetation which mostly depend on the groundwater, the main source of irrigation water as well.Our study presented an example of the utility of spatially and temporally continuous RS data in assessing the regional trends in hydrological and ecological variables and their interactions in a spatially distributed manner in a semi-arid region, which can also be adapted to other regions. Such spatiotemporally distributed analysis at the basin level is particularly important considering that most of the water management interventions also take place at this scale.

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Climate Signal Detection Times and Constraints on Climate Benchmark Accuracy Requirements

Cited by 80 publications

References 5 publications

Quantification of structural uncertainty in climate data records from GPS radio occultation

Quantification of structural uncertainty in climate data records from GPS radio occultation

Accurate radiometry from space: an essential tool for climate studies

Satellite-based analysis of recent trends in the ecohydrology of a semi-arid region

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