* In February, 2006 NCDC transitioned to the use of an improved Global Land and Ocean data set (Smith and Reynolds analysis (2005)-RRB- which incorporates new algorithms that better account for factors such as changes
in spatial coverage and evolving observing methods.
Last year, an analysis conducted by the UK Met Office demonstrated that the disagreement amongst groups arose primarily from the differences
in spatial coverage, especially the inclusion or exclusion of polar regions.
The instrumental record before then is hideously insufficient
in spatial coverage of the planet to establish a global average temperature.
The processing of these observations is straightforward, but large gaps
in spatial coverage compromise the reliability of global averages, and changes in instrumentation can give rise to spurious trends.
Since 1900, the change
in spatial coverage does not seem to have affected land records significantly.2 Before then, however, even careful analysis may lead to long - term averages that are either too warm or too cold by up to 0.1 C. 1 Records may be affected by changes in the way observations are made.
Not exact matches
SUVI replaces the GOES Solar X-ray Imager (SXI) instrument
in previous GOES satellites and represents a change
in both spectral
coverage and
spatial resolution over SXI.
However, the Hadley Centre SST data set60, 61 (HadSST3, v3.1.1.0) is not global
in coverage: rather than interpolating over all space and time coordinates it consists of
spatial means within 5 ° × 5 ° bins, leading to missing values
in the absence of data.
Statisticians can advise on how best to combine data from different sources, how to identify and adjust for biases
in different measurement systems, and how to deal with changes
in the
spatial and temporal
coverage of measurements.
One approach is to develop empirical regional models that enable aragonite saturation state to be estimated from existing hydrographic measurements, for which greater
spatial coverage and longer time series exist
in addition to higher
spatial and temporal resolution.
In this case, there has been an identification of a host of small issues (and, in truth, there are always small issues in any complex field) that have involved the fidelity of the observations (the spatial coverage, the corrections for known biases), the fidelity of the models (issues with the forcings, examinations of the variability in ocean vertical transports etc.), and the coherence of the model - data comparison
In this case, there has been an identification of a host of small issues (and,
in truth, there are always small issues in any complex field) that have involved the fidelity of the observations (the spatial coverage, the corrections for known biases), the fidelity of the models (issues with the forcings, examinations of the variability in ocean vertical transports etc.), and the coherence of the model - data comparison
in truth, there are always small issues
in any complex field) that have involved the fidelity of the observations (the spatial coverage, the corrections for known biases), the fidelity of the models (issues with the forcings, examinations of the variability in ocean vertical transports etc.), and the coherence of the model - data comparison
in any complex field) that have involved the fidelity of the observations (the
spatial coverage, the corrections for known biases), the fidelity of the models (issues with the forcings, examinations of the variability
in ocean vertical transports etc.), and the coherence of the model - data comparison
in ocean vertical transports etc.), and the coherence of the model - data comparisons.
Moreover, few of the sondes are
in the inner tropics,
spatial coverage is spotty, and there are questions of instrumental and diurnal sampling errors that may have complicated detection of the trend
in the past decade.
First impressions are that this has a number of artifacts
in it likely due to inhomogeneities
in the satellites (varying levels of
spatial coverage through time as satellites drop
in or out).
But the bias uncertainty is smaller than the errors which are not persistent
in time (e.g. due to incomplete
spatial coverage), so I don't think accounting for this would make much difference, as Victor suggests.
The figure to the left shows the
spatial mean temperature over all grid boxes
in the HadCRUT3 data set that have continuous monthly
coverage over the 1901 - 2008 period.
This product is consistent with broad current knowledge about the surface sources and sinks of CO2, CH4 and N2O, but, to our knowledge, it is unique
in its combination of temporal
coverage,
spatial resolution and inclusion of recent measurements.
Shifts and trends
in plankton biomass have been observed for instance
in the North Atlantic (Beaugrand and Reid, 2003), the North Pacific (Karl, 1999; Chavez et al., 2003) and
in the Southern Indian Ocean (Hirawake et al., 2005), but the
spatial and temporal
coverage is limited.
But I suppose we can leave that to a study of the proper way of calculating a error due to
spatial coverage, that error will be a function (at least
in the math I've seen) involving the
spatial correlation which varies considerably.
Two thermometers along the Atlantic coast of North America, three thermometers
in central Europe, one
in England, and one by the Great Lakes is not sufficient
spatial coverage to make claims about the temperature of the Middle East, India, China, Japan, Mexico, etc..
In general,
spatial and temporal coincidences offered by the Dobson and Brewer networks are sufficient to cover a wide geographical extent for the validation of a satellite sensor, however, with better
coverage over land with respect to sea and over the Northern Hemisphere compared to the Southern Hemisphere.
The flux estimates presented
in previous sections use available estimates from every reservoir where GHG emissions have been reported (and mean estimates from reservoirs where multiple studies or years of data have been collected), but it is important to note that the
spatial and temporal
coverage of these emission estimates are highly variable.
Precipitation and soil moisture are both presented using two different data records that are complementary
in terms of
spatial coverage and
spatial resolution.
«Bias might be introduced
in cases where the
spatial coverage is not uniform (e.g., of the 24 original chronologies with data back to 1500, half are concentrated
in eastern Siberia) but this can be reduced by prior averaging of the chronologies into regional series (as was done
in the previous section)... Eight different methods have been used... They produce very similar results for the post-1700 period... They exhibit fairly dramatic differences, however,
in the magnitude of multidecadal variability prior to 1700... highlighting the sensitivity of the reconstruction to the methodology used, once the number of regions with data, and the reliability of each regional reconstruction, begin to decrease.
«The addition of buoy data
in recent decades has been particularly important as the
spatial coverage from ship observations has decreased since the 1990's (cf. Fig. 1 (a)
in (13)-RRB-.
The difference
in the latter aspect is most likely due to improvement
in the
spatial — temporal
coverage of the data used
in this study, as well as the details of data processing procedures.
Beginning
in 1979 we have the satellite record which is really the only sensor system I feel is adequate
in accuracy, precision, and especially
spatial coverage to measure global average trend to a precision of hundredths of degrees per decade.
Another avenue for monitoring is satellite measurements of column inventories of the gases, which provide much more detailed
spatial coverage but no vertical resolution,
in which air masses at different altitudes may carry gases that originated from different parts of the Earth's surface.
Spatial coverage is pitifully inadequate, misses the oceans which are the real climate drivers, no discipline
in siting, calibration, no repeatibility, amateur volunteers doing all the heavy lifting... A fool's errand trying to make a silk purse from a sow's ear.
The challenges are finding a good enough measure of urbanity, dealing with uncertainty
in station locations (a problem
in many areas outside the U.S., where lat / lon coordinates aren't always accurate), and ensuring that your method doesn't suffer from
spatial coverage biases between urban and rural sets (I tend to prefer station pair comparison methods for that reason).
But use enough weather stations, and your answer is not only better because you have better
spatial coverage, but because errors — even pretty large errors —
in one of the weather stations probably won't affect your result.
Key challenges, therefore, will be to increasingly: 1) interrogate extreme events
in climate simulations; 2) use earth system models to disentangle the complex and multiple controls on proxies; 3) adopt multi-proxy approaches to constrain complex phenomena; and 4) increase the
spatial coverage of such records, especially
in arid regions, which are currently under - represented.
Because of their large
spatial coverage, satellite data have proven useful
in evaluating dust sources, transport and deposition
in global models.
Prior to 1988, the satellite data that Trenberth uses is not available, but it is known that long term records
in radiosondes contain large inhomogeneities due to improving observing systems, increasing
spatial resolution (but still very little ocean
coverage), and the NCEP data
in particular contains large model biases.
To say that the pre-satellite humidity trends are correct, despite the many changes
in instrumentation, despite the changes
in spatial and temporal resolution (but still almost no ocean
coverage), despite the known problems with NCEP model bias, and despite that it has been wrong throughout the satellite era... well, it's ludicrous.
However there are limited long - term air concentration datasets and significant gaps
in the
spatial and temporal
coverage (Keeler et al., 2009).