The GISS data for world temperatures go back to 1880. Can the old data really be compared to today's temps?

Question

Given the vast differences in temperature recordation technology between the 1800s and today, how do we even know whether or not the temperatures measured had the same reliability back then? What in the GISS data accounts for the inherent inconsistencies in data collection?

Answer 1

yes they are very good

Answer 2

Not exactly, but the difference isn't enormous.  The data isn't as reliable, but it's not totally unreliable either.  Scientists have a fair handle on how reliable it is.

This data from GISS shows that analysis.  The green "error" bars show the uncertainty in temperature.  They get larger as you move backwards, but they don't destroy the graph.

A basic scientific fact is that, up to a point, you can improve accuracy by averaging a lot of data.  The graph and the analysis of the data gives some confidence that we're not way off.

http://data.giss.nasa.gov/gistemp/2007/

Answer 3

It's a poor theory that relies on a single source of information. When the data correlate with tree ring measurements and ice core measurements, you can be fairly sure that they are accurate.

Answer 4

The main problem with the Science in the this field is the lack of data and the quality of data.  But yes old data can be compared to today's data.  It helps scientists to establish trends.  Now we are able to drill polar ice caps and by using the oxygen isotopes we can determine what they temperature was during the period when the air was first trapped in the ice.  This will give us a much better data set for scientists to establish good evidence to substantiate global climate change.

Answer 5

This is a good question but you won't find an honest answer. GISS continually 'corrects' temp data until it achieves the end result they want, just as they ignore CO2 readings that disagree with AGW theory.

It's been possible to measure temp for a long time, and the same is true of CO2. Yet direct observations of CO2 levels have been ignored since they don't fit the current theory.

"Direct atmospheric measurements indicate that between 1812 and 1961, the concentrations of CO2 fluctuated by about 150 ppmv, up to values much higher than those of today. Except for the year 1885, these direct measurements wer always higher than the ice core data, which are devoid of any variations. During the 149 years from 1812 to 1961, there were three periods when the average CO2 concentration was much higher than it was in 2004, 379 ppmv (IPCC 2007): Around the year 1820, it was about 440 ppmv; around 1855, it was 390 ppmv; and around 1940, it was 440 ppmv. Data compiled by Beck (Beck 2007) suggest also that changes of the CO2 atmospheric concentration followed, rather than preceded, the temperature changes."

How does this jibe with global warming theory? It doesn't because CO2's input into warming is overstated. Given laboratory conditions you can demonstrate a clear relationship between CO2 levels and temp, but in the real world such a relationship does not exist because it is a weak contributor to global temp and cannot change long-term trends.

Here's an excerpt from the summary of actual and direct CO2 measurements, titled 180 years accurate CO2 air gas analysis by chemical methods. It does not agree with ice core data regarding CO2 levels.

"1. There is no constant exponential rising CO2-concentration since preindustrial times but a varying CO2-content of air following the climate. E.G. around 1940 there was a maximum of CO2 of at least 420 ppm, before 1875 there was also a maximum.

2. Historical air analysis by chemical means do not prove a preindustrial CO2-concentration of 285 ppm (IPCC),as modern climatology postulates. In contrast the average in the 19th century in northern hemisphere is 321 ppm and in the 20th century 338 ppm.

3. Todays CO2 value of. 380 ppm, which is considered as threatening has been known several times in the last 200 years, in the 20 th century around 1942 and before 1870 in

the 19th century. The maximum CO2-concentration in the 20th century roses to over 420 ppm in 1942."

Answer 6

It's still based on actual land measurements for only about 1/3 of the globe.  Much is based on estimates based on satellite data and other estimates.  The first weather satellite was sent up in April 1960.

We have a pretty good idea that it's about 1 degree F warmer than it was in 1880 - when we were starting to emerge from the Little Ice Age.    The notion that you can rank the years and assign values in the tenths of a degree F, before a quarter century ago, and that that's anything more than a guess, is silly.

Kent points out the efforts to correlate proxy measurement techniques with current measured temperatures - except that many of the assumptions about past climate are based on proxy techniques that don't correlate with current measured temperatures - i.e., pine tree rings.

Before the climate became a political issue, past climates were reconstructred relying primarily on direct evidence - what grew when and where.    A species thriving in the past where it is too cold to survive today, higher crop yields, crops being grown where they can't grow today, and glacial retreat all were interpreted to mean it was warmer.   And before the climate became a political issue, everyone agreed that within human history there were certain warmer periods, as well as periods almost as warm, each lasting for centuries, despite lower CO2 concentration.    

Proxy models based on pine tree rings - from about a dozen pine trees by the way, not hundreds - make the most recent warm period disappear from the climate history.    There is other proxy data but it's only the pine tree rings that make the most recent prior warm period disappear.  

The IPCC, in 1998, a year after the death of the leading paleoclimatologist, Hubert Lamb, whose reconstruction based primarily on direct evidence had been univerally accepted and had clearly shown the prior warm periods, abuptly abandoned that reconstruction for one based on the pine tree rings.

They never attempted to explain away any of the direct evidence to which Lamb pointed - severe, prolonged and widespread droughts, lakes drying up that aren't dry now, agricultural records, settlement of land now frozen over, higher tree lines, etc.....    They dismissed this evidence as "anecdotal" and "regional" but the "anecdotes" cover centuries and they are from almost every "region" of the globe.

Somehow a model based upon assumptions concerning the relationship of temperature to the widths of the rings of a dozen or so trees that grew in the same place then and now trumped the worldwide evidence of what grew when and where.

But the tree ring data extended only to 1980 - when the warming that the IPCC views as being "unprecedented" began to occur.

Those who had created models using tree rings didn't want to update the tree ring samples to see if in fact they did correlate to the modern rising temperatures - to see if their assumed relationship between temperature and tree ring widths was actually even correct.

Some analysts have updated some of the samples - and guess what, the assumed correlation is wrong.   Beyond a certain point the tree rings don't get wider with higher temperature.

That means the absence of wider tree rings during the MWP doesn't mean it wasn't warmer.

So I ask you - and anyone - why we should ignore the actual physical evidence of what grew when and where and instead rely on a computer model using proxy data in a way that is based on wrong assumptions about the relationship of that proxy data to temperature?

There is only one reason to do so - because that produces the results you want to see.

Answer 7

Human reader accuracy and global coverage are other challenges:

"There was not much overall change from 1850 to about 1915, aside from ups and downs associated with natural variability but which may have also partly arisen from poor sampling."

"It is now possible to use these measurements from 1850 to the present, although coverage is much less than global in the second half of the 19th century, is much better after 1957 when measurements began in Antarctica, and best after about 1980, when satellite measurements began."

There are lots of other data sets and observations that are consistent with the theory, so it's not like everything's hinging on a few old mercury thermometer readings:

"An increasing rate of warming has taken place over the last 25 years, and 11 of the 12 warmest years on record have occurred in the past 12 years. Above the surface, global observations since the late 1950s show that the troposphere (up to about 10 km) has warmed at a slightly greater rate than the surface, while the stratosphere (about 10–30 km) has cooled markedly since 1979. This is in accord with physical expectations and most model results. Confirmation of global warming comes from warming of the oceans, rising sea levels, glaciers melting, sea ice retreating in the Arctic and diminished snow cover in the Northern Hemisphere."

Answer 8

The mercury thermometer was invented in 1714 and the physical properties of mercury haven't changed since then.  The coverage area (how many measurements per region) has certainly grown over time, but there are a variety of numerical analysis techniques (long used in various branches of science) that can account for missing data.

There are actually some regions which have a pretty solid temperature history going back well before 1880.  There's a continuous central england temperature record that actually predates the mercury thermometers (to the mid 17th century) but it's accuracy is clearly not up to 19th century standards.

But confidence grows and error bars shrink, as you're able to correlate various proxy temperature measurement techniques with modern instrumentation and then use those same proxy methods to validate earlier instrumentation records (when we didn't have as complete coverage of the surface as we now have.

Answer 9

Not only that, good point, but what does 120 years tell anyone about a trend in the Earths climate?

The believers look at such a very short period of the history of Earth and make a long term trend.  It's just foolish.