Maggie's Farm

steveaz: These people think you can turn a knob and the earth's temperature will mirabile dictu conform.

Climate scientists do not make that claim. Greenhouse gases are only one factor influencing the Earth's mean surface temperature. On the other hand, as paleoclimatologists have shown, the history of Earth's climate requires accounting for greenhouse gases.

faculty wife: the thousands of planes in the air at any one 24 hour period--you know BOEING. Nope they won't touch that subject with any serious effort!

Aircraft contribute about 2.5% of current global emissions of greenhouse gases, 4% of accumulated emissions. And yes, aviation is an important issue for environmentalists. The International Civil Aviation Organization has committed to reducing emissions.

BenDavid: Human-generated carbon and carbon dioxide are a rounding error compared to the natural processes that exchange billions of tons of oxygen, nitrogen, and carbon between earth, air and oceans.

Natural gas exchanges have a generally net zero effect on the atmospheric concentration of greenhouse gases. However, anthropogenic greenhouse emissions have led to an increase in the atmospheric concentration.

BenDavid: The main driving force for changes in these processes is solar radiation - which also fluctuates.

Changes in insolation do not explain the current warming trend, which actually indicate a slight cooling trend.

BenDavid: None of these processes are any where near an extreme value compared to earth's history.

True enough, but it's not as if humans would want to see a rapid change to the Cretaceous hot greenhouse environment.

Ray: I would like to find out how they average temperature since temperatures do not add.

If you have a kg of water at 80°C and a kg at 40°C, then when you mix them, you will have two kg of water at 60°C. Given that the atmosphere is relatively well-mixed, you can estimate the average dry-air temperature. Otherwise, you would be left with the preposterous claim that you can't distinguish between the average surface temperature of Mars and Venus or between the tropics and the arctic.

You can also determined the mixed temperature of two heterogeneous liquids by weighting temperature by thermal mass. And in many complex cases, you can use additive energy.

Bird Dog: the worst is taking a global temperature.

Global temperature can be estimated. For instance, global temperatures were much lower during the last glacial period, but much higher during the Cretaceous Thermal Maximum. In any case, scientists studying anthropogenic global warming generally use temperature anomalies, which have a much lower error margin that absolute temperature (which have a high error rate due to uneven coverage).

While one might think that surface temperature measurements are fraught with error, the observed surface trend is supported by multiple independent means, including satellite observations, ocean heat content observations, observations of the cryosphere, and the fundamental physics of the greenhouse effect. All these scientific means show the same sign and approximate degree of global warming.

Cooter: What is the global mean surface temperature of the Earth SUPPOSED to be?

It's not "SUPPOSED" to be anything. However, human civilization evolved within a narrow range of climate conditions. Rapid change would be detrimental to modern humans who have built huge infrastructure (cities, transportation, agriculture, etc.) that depend on relative climate stability, especially on coastlines, rivers, and fertile basins.

Now, you might ask, why are humans SUPPOSED to be? After all, homo sapiens are just one of many species that have come and gone on the Earth over the eons. Well, we are rather fond of the humans. Call it a peccadillo, if you like.

Cooter: When climate scientists deem a warming threshold that must not be exceeded of 1.5 deg C, then, yes, they are implying a global average surface temperature that we must maintain.

That's right. When Earth's mean temperature suddenly (over a few decades) increases by 1.5-2.0°C, it will result in vast changes and instabilities to the climate, with detrimental effects to humans. Consider just the change in sea level. About two billion people live close to a coastline, huge cities built there for sea trade and agriculture along fertile coastal plains, among many reasons. It's the change that's the issue. If the sea levels were already higher in the past, but remained stable, then cities would have been built at that level. But they weren't.

Now, if global warming were inevitable, then humans would have no choice but to adapt, no matter how costly. In this case, though, the warming is human caused. (It's the equivalent of sh!tting where you live.) One of the results will be mass migration. Consider how much political and social friction is already due to human migration—even in liberal countries, such as the United States. Now, consider what happens when migration patterns encompass billions of people.

Cooter: What is that temperature?

Earth's mean temperature is about 15°C and rising. But it's the rapid warming and the chaotic climatic changes due to the rapid rise that will be the issue for humans over the next century.

Cooter: ...are based on mathematical modeling/computer simulations

Your original position was something something “SUPPOSED to be”. As for your new tack, virtually all science is about models, so that is as vacuous as your previous position.

Cooter: and we have 50 years of failed predictions.

Study Confirms Climate Models are Getting Future Warming Projections Right

Cooter: Meteorologists, with real-time data, cannot predict the path of a hurricane, a local phenomenon, and therefore display the hurricane path as a "cone of uncertainty."

Not knowing everything is not the same as not knowing anything. Hurricanes are inherently chaotic. That doesn't mean we have no knowledge of their paths, and modern projections are considerably better than even a generation ago, saving lives.

Cooter: And yet, climate scientists can predict to one TENTH of one degree Celsius, the temperature anomaly . . ..

The temperature anomaly is something that can be measured with considerable precision. If a hundred observational stations show warming, what is the likelihood that this is due to random observational error? Even simpler, if we take a hundred measurements of the same phenomenon, each with a margin of error of ±1, given random observational error, what is the precision of the mean of those measurements?

Cooter: a global phenomenon with innumerable factors, interactions and feedback loops

You are conflating the observed temperature anomaly with projections. You are also confusing global warming with climate change. Global warming is strongly established, and the warming is very likely 2-4°C per doubling of atmospheric carbon dioxide. However, how this excess heat will be distributed through the climate system is inherently chaotic and less certain. To use an analogy: When bringing a pot of water to boiling on a stove, we can predict how long it will take and how much water will turn to steam over time; however, we can't predict with precision where the individual bubbles will form.

Cooter: that will be an existential threat to humanity.

Global warming is not a direct existential threat to humanity. Humans are highly adaptable. Part of that adaptability; however, comes from their ability to project the future and take actions to forestall the worst effects. There is little remaining scientific doubt that global warming will bring about significant and dangerous climate change. The sooner humans mitigate the problem, the less the economic damage, the lower the cost in terms of humanity's shared ecological inheritance, and the less chance that social and political frictions due to climate change will result in violent conflict.

Aggie: The real tragedy is that our ability to understand our climate has been compromised deliberately, by a willingness to manipulate data and present bad science as a result

What makes you think that UAH has improperly manipulated the satellite data?

Ray: Temperature is an intrinsic parameter and it does not depend on mass. It is not additive like joules.

Temperature is directly related to the average kinetic energy (in joules if you like). Consequently, with a homogeneous substance, averaging temperatures is the equivalent of averaging kinetic energy. For instance, if you have a kg of water at 80°C and a kg at 40°C, then when you mix them, you will have two kg of water at 60°C. Similarly, the average temperature of Paris in summer is higher than in winter.

You might want to consider the latter statement about Paris. Are you really claiming that "the average temperature of Paris in summer is higher than in winter" is meaningless, or does it make empirical predictions about the air temperature in Paris? If we were to test the claim by observing the temperature in Paris in summer and winter on various days, would the claim likely be confirmed? It's clear the statement has empirical meaning—and, in this case, it happens to be true.