Scientists looked at changes in the length of hundreds of glaciers measured over the course of the twentieth century. Money quote:
The temperature record obtained from glacier fluctuations confirms the pronounced warming of the twentieth century, giving a global cumulative warming of 0.94 ± 0.31 K over the period 1830–2000 and a cumulative warming of 0.84 ± 0.35 K over the period 1600–2000.
The pronounced warming of the last hundred years is old news to most of us, but sixty percent of climate deniers still think the world is not warming at all. Among many others, there circulates the myth that climate science is merely a collection of computer models:
"More Trouble For Global Warming Alarmists":
Because global warming alarmism is based almost entirely on computer climate models rather than, you know, actual scientific observation. The models have already been shown to be unable to accurately predict historical climate changes on a backward looking basis for periods in which we have observational data. Now, they are once again proven wrong. Garbage in; garbage out.
"Joe Dallas" repeats the meme:
The alarmists’ claims are based entirely on hypothetical indirect consequences of additional CO2. But these alleged indirect effects are not based on empirical observation, they are merely hypothesized by the alarmists and incorporated into their computer models. For a long time, we have known that the models’ predictions are contradicted by empirical observation. In the world of science, this is called refutation of a theory, but global warming exists in the realms of politics and religion, not science.
"Abovetopsecret," a favorite hangout of mass murderer/climate denier Anders Behring Breivik, ties this myth to Roy Spenser's latest modelling misadventure:
In order for human emissions to cause any real change in climate, alarmist scientists have to incorporate “feedback” mechanisms in their models that greatly amplify the known effects of human CO2 warming.
These “feedback” mechanisms are entirely hypothetical constructs which are incorporated into alarmist computer models.
The fact that this commenter, like so many others, uses a paper that is no more than curve fitting a crude and poorly executed model, to criticize the use of computer models, is an indication of how ill-thought-out (or deceptive) these criticisms are. And the hypocrisy is widespread. Not just Roy Spencer's recent paper but any sort of computer model that produces results deniers like garners almost delirious praise, with all their former skepticism of "computer models" temporarily forgotten.
The truth of the matter is that scientists are still very much in the business of observing the physical world. Take just one variable, global temperatures over time, and you will find scientists measuring it in every conceivable way you can think of and more than a few that never occurred to you. A partial and incomplete list:
!. Direct temperature measurements at fixed sites.
2. Changes in the ranges of plant and animal life.
3. Changes in sea level.
4. Changes in glacier size, mass, and distribution.
5. Direct measurements of outgoing radiation and incoming radiation at the top of the atmosphere.
6. Changes in the shape of the earth (really!)
7. Changes in plant growth (like tree ring data).
8. The isotopic composition of snow, corals, and stalactites.
9. Sediment core records of Arctic lakes.
10. Ice core data.
11. Flood markings.
12. Records of crop and grape harvests.
13. Weather diaries and historical maps.
14. Records documenting the timing and extent of Christian agricultural celebrations.
15. Instrumental records of humidity (which varies directly with temperature).
16. Satellite measurements.
The list goes on and on. All these data sources, like all data, has strengths and weakness and limited resolution. That is not my point. What the data proves and what it doesn't is a discussion for another day. My point is that scientists measure things, and climate scientists measure things a lot -- many different kinds of things, collecting information over large spans of time. Once those data sets exist, computer models become an essential adjunct in understanding the data and what is says about our climate and our future. But let's not lose sight of who is spending long hours at low pay collecting real observations from nature, and who is obsessively mathturbating.