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Also worth mentioning that there are at least three major 'systems' in play here
1) Human activity contributing to Global warming by increased activity and thus greenhouse gases 1a) Human activity changing the usage of land on Earth and depleting some other species to the extent of extinctions (as well as more grazing animals contributing methane to greenhouse gases as in 1) 2) The solar cycle 3) Geological processes
Also worth mentioning that there are at least three major 'systems' in play here
1) Human activity contributing to Global warming by increased activity and thus greenhouse gases 1a) Human activity changing the usage of land on Earth and depleting some other species to the extent of extinctions (as well as more grazing animals contributing methane to greenhouse gases as in 1) 2) The solar cycle 3) Geological processes
Indeed, it is an immensely complicated field.
I just think it is fascinating that at the end of the 70s it was an ice age that was the climate worry and scientists were reporting 30 years of falling temperatures, whereas now it is the other way round.
There has been a dramatic reversal of opinion over the last few decades on 11:37 - Dec 7 by GeoffSentence
Indeed, it is an immensely complicated field.
I just think it is fascinating that at the end of the 70s it was an ice age that was the climate worry and scientists were reporting 30 years of falling temperatures, whereas now it is the other way round.
Bloody scientists heh!!
"They break our legs and tell us to be grateful when they offer us crutches."
There has been a dramatic reversal of opinion over the last few decades on 11:37 - Dec 7 by GeoffSentence
Indeed, it is an immensely complicated field.
I just think it is fascinating that at the end of the 70s it was an ice age that was the climate worry and scientists were reporting 30 years of falling temperatures, whereas now it is the other way round.
This is complicated, but basically the premise of this thread isn't correct. In the early 70s there were some prominent scientists who calculated that the cooling effect of aerosols would outweigh the warming effect of CO2 in the atmosphere, but these were very, very early, primitive attempts to model the climate. Add in a few cold winters, and you ended up with some hyperbolic reporting like that.
Actually though, even in the late 70s there was a fairly strong consensus that the Earth was going to warm. Despite enormous limitations (compared to now) on datasets, computing power, and modelling techniques, in 1979 the Charney Report summarises the state of climate science (which had basically only existed as a discipline for a few years) - and the conclusions are strikingly consistent with what we now know (the bit about higher latitudes, particularly):
"When it is assumed that the CO2 content of the atmosphere is doubled and statistical thermal equilibrium is achieved, the more realistic of the modeling efforts predict a global surface warming of between 2°C and 3.5°C, with greater increases at high latitudes. This range reflects both uncertainties in physical understanding and inaccuracies arising from the need to reduce the mathematical problem to one that can be handled by even the fastest available electronic computers. It is significant, however, that none of the model calculations predicts negligible warming."
[Post edited 7 Dec 2019 12:12]
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There has been a dramatic reversal of opinion over the last few decades on 12:32 - Dec 7 with 580 views
There has been a dramatic reversal of opinion over the last few decades on 12:11 - Dec 7 by gordon
This is complicated, but basically the premise of this thread isn't correct. In the early 70s there were some prominent scientists who calculated that the cooling effect of aerosols would outweigh the warming effect of CO2 in the atmosphere, but these were very, very early, primitive attempts to model the climate. Add in a few cold winters, and you ended up with some hyperbolic reporting like that.
Actually though, even in the late 70s there was a fairly strong consensus that the Earth was going to warm. Despite enormous limitations (compared to now) on datasets, computing power, and modelling techniques, in 1979 the Charney Report summarises the state of climate science (which had basically only existed as a discipline for a few years) - and the conclusions are strikingly consistent with what we now know (the bit about higher latitudes, particularly):
"When it is assumed that the CO2 content of the atmosphere is doubled and statistical thermal equilibrium is achieved, the more realistic of the modeling efforts predict a global surface warming of between 2°C and 3.5°C, with greater increases at high latitudes. This range reflects both uncertainties in physical understanding and inaccuracies arising from the need to reduce the mathematical problem to one that can be handled by even the fastest available electronic computers. It is significant, however, that none of the model calculations predicts negligible warming."
[Post edited 7 Dec 2019 12:12]
Thanks for that excellent and informed response.
I don't want to come across as a climate change denier, I'm not I think we are poisoning our planet in all sorts of different ways, but there are some things that I don't understand, like the statement in that documentary that scientists measured northern hemisphere temperatures had been declining for 30 years, 2 degrees of lowering temperatures in the arctic for instance. Is that science accurate?
Another one being the proxy temperature data showing a drop in temperatures over the last thirty years, the subject of the climategate 'nature trick', so given that we have proxy data diverging from real measured data, how can the archaic temperature record based on proxy data be trusted?
There has been a dramatic reversal of opinion over the last few decades on 12:32 - Dec 7 by GeoffSentence
Thanks for that excellent and informed response.
I don't want to come across as a climate change denier, I'm not I think we are poisoning our planet in all sorts of different ways, but there are some things that I don't understand, like the statement in that documentary that scientists measured northern hemisphere temperatures had been declining for 30 years, 2 degrees of lowering temperatures in the arctic for instance. Is that science accurate?
Another one being the proxy temperature data showing a drop in temperatures over the last thirty years, the subject of the climategate 'nature trick', so given that we have proxy data diverging from real measured data, how can the archaic temperature record based on proxy data be trusted?
It was the so called 'hockey stick trick' wasn't it? Came out of the UEA so did have a bit of Norfolk clumsiness about it but a minor infringement that was seized upon and ramped up by the deniers. I think it can be said that their line of attack is fairly unscientific and would be more acceptable if it were balanced.
The second graph on the document from a United States national agency does not seem to support the assertion of a cooling climate in the middle of the Twentieth century:
There has been a dramatic reversal of opinion over the last few decades on 12:32 - Dec 7 by GeoffSentence
Thanks for that excellent and informed response.
I don't want to come across as a climate change denier, I'm not I think we are poisoning our planet in all sorts of different ways, but there are some things that I don't understand, like the statement in that documentary that scientists measured northern hemisphere temperatures had been declining for 30 years, 2 degrees of lowering temperatures in the arctic for instance. Is that science accurate?
Another one being the proxy temperature data showing a drop in temperatures over the last thirty years, the subject of the climategate 'nature trick', so given that we have proxy data diverging from real measured data, how can the archaic temperature record based on proxy data be trusted?
I can't really speak to what's in that documentary because it isn't referenced, but those numbers sound too big - although there was a period from the 1940s to the 1970s when temperatures remained stable or cooled (see the graph at the second link), leading to the stuff in that documentary.
Just for interest though, here's a link to a paper written in 1972 which predicted an increase in global mean teperature of 0.6 degrees by 2000. Observed warming was actually about 0.54 degrees - the reason for the slight over-estimate was that the paper slightly overestimates how much CO2 was going to be emitted (so the model, even back then, was pretty accurate).