I know that some icers on the Alps have been shrinking since the last 120 years (more or less since we started measuring them) a bit too early IMO for humans to be the cause, yet the melting has significantly accelerated in the last 30-40 years (which is likely to be correlated to human activities)
Sure. We’ve taken ice cores out of glaciers that are super long. Basically there’s an isotope of Oxygen that strongly correlates to air temperatures that we can measure at different levels of the core. We know roughly how much ice gets deposited onto the glacier every year so we can extrapolate how long ago each layer was deposited and then measure that isotope to get an estimate of how warm it was that winter going back a few thousand years. Taking that data and combining it with modern temperature readings we can see a sharp uptick around the late 19th century where increased human greenhouse gas output begins.
But that’s about the local temperature of the year, it says nothing about the glaciers shrinking or expanding, also if glaciers are shrinking, wouldn’t we lose some readings? I mean if the glacier this year is smaller than last year, means that we have lost at least one year readings (most likely much more than that), not to mention that it contradicts that ice gets deposited every year.
It is my understanding that glaciers expand and shrink seasonally every year, and lately the expansion (if any) is always smaller than the shrinking, but it is a trend that started more than 100y ago (basically since when we started keeping record) and has been accellerating, because of this how can you extrapolate when to start dating in reverse? If you never saw a the, let’s call it inflationary phase, how do you know when it reversed? The error might be small… or not
Is there an error in my reasoning (or my assumptions)? Consider that I am not the only one having this doubts.
Most of the glacial loss, especially on higher elevations, is from sublimation and not directly melting. That doesnt cause the loss of the measurable isotopes.
Can you elaborate a bit?
I know that some icers on the Alps have been shrinking since the last 120 years (more or less since we started measuring them) a bit too early IMO for humans to be the cause, yet the melting has significantly accelerated in the last 30-40 years (which is likely to be correlated to human activities)
Sure. We’ve taken ice cores out of glaciers that are super long. Basically there’s an isotope of Oxygen that strongly correlates to air temperatures that we can measure at different levels of the core. We know roughly how much ice gets deposited onto the glacier every year so we can extrapolate how long ago each layer was deposited and then measure that isotope to get an estimate of how warm it was that winter going back a few thousand years. Taking that data and combining it with modern temperature readings we can see a sharp uptick around the late 19th century where increased human greenhouse gas output begins.
But that’s about the local temperature of the year, it says nothing about the glaciers shrinking or expanding, also if glaciers are shrinking, wouldn’t we lose some readings? I mean if the glacier this year is smaller than last year, means that we have lost at least one year readings (most likely much more than that), not to mention that it contradicts that ice gets deposited every year.
It is my understanding that glaciers expand and shrink seasonally every year, and lately the expansion (if any) is always smaller than the shrinking, but it is a trend that started more than 100y ago (basically since when we started keeping record) and has been accellerating, because of this how can you extrapolate when to start dating in reverse? If you never saw a the, let’s call it inflationary phase, how do you know when it reversed? The error might be small… or not
Is there an error in my reasoning (or my assumptions)? Consider that I am not the only one having this doubts.
Most of the glacial loss, especially on higher elevations, is from sublimation and not directly melting. That doesnt cause the loss of the measurable isotopes.