Hmmm. I wonder why that graph started in 1970 and ended in 2004? The temperature changes would almost be nonexistent if you started in 1930 and ended in 2008.

Wrong. The Fourth Assessment Report of the IPCC documents that temperatures grew over the past 100 years--perhaps even the past 150 years:

Fourth Assessment Report said:

Eleven of the last twelve years (1995-2006) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850)...The linear warming trend over the 50 years from 1956 to 2005 (0.13 [0.10 to 0.16]°C per decade) is nearly twice that for the 100...

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Hmmm. I wonder why that graph started in 1970 and ended in 2004? The temperature changes would almost be nonexistent if you started in 1930 and ended in 2008.

Wrong. The Fourth Assessment Report of the IPCC documents that temperatures grew over the past 100 years--perhaps even the past 150 years:

Fourth Assessment Report said:

Eleven of the last twelve years (1995-2006) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850)...The linear warming trend over the 50 years from 1956 to 2005 (0.13 [0.10 to 0.16]°C per decade) is nearly twice that for the 100 years from 1906 to 2005. (page 30)

The report has a nice graph showing the trends in average global surface temperatures, sea level, and Northern hemisphere snow cover.

It is simple math. The hottest year in the past half century was 1998. It hasn't been hotter since, and it is cooler now than it was then so we have been on a decade long cooling trend. And even inside that decade it has been multiple trends. We cooled for a few years after 1998, then warmed back up in 2002, and have been cooling ever since then.

But if you go further back, the warmest year in the past century was 1935. It was warmer in the 1930s, when our output of CO2 was much lower than it is now. Then there was a cooling trend that started in the 1940s and ended in the 1970s. The main reason they pick the 1970s is that they were at the tail end of a decades long cooling trend that had t...

It is simple math. The hottest year in the past half century was 1998. It hasn't been hotter since, and it is cooler now than it was then so we have been on a decade long cooling trend. And even inside that decade it has been multiple trends. We cooled for a few years after 1998, then warmed back up in 2002, and have been cooling ever since then.

But if you go further back, the warmest year in the past century was 1935. It was warmer in the 1930s, when our output of CO2 was much lower than it is now. Then there was a cooling trend that started in the 1940s and ended in the 1970s. The main reason they pick the 1970s is that they were at the tail end of a decades long cooling trend that had the scientific community preaching the doom and gloom of a coming ice age.

And if you want to draw that point that the Earth was warming 150 years ago, that kinda hurts the argument that global warming is man made since that was well before the industrial revolution. The climate changes, that's what it does. Those who believe that every little change in the Earth's temperature is man made is delusional.

n2sooners said:

The hottest year in the past half century was 1998.

OK, I see Wilhelm's point now. IPCC graph does show 1998 as the hottest year since 1850.

n2sooners said:

we have been on a decade long cooling trend.

This conveniently ignores the fact that the past decade has been the hottest in the past 150 years.

n2sooners said:

It was warmer in the 1930s

I see no evidence for this, nor any evidence for your assertion that 1935 was the hottest year in the century. The graph shows an upswing in temperatures in the 1930s, but nothing that is comparable to what happened since the 1970s.

n2sooners said:

And if you want to draw that point that the Earth...

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n2sooners said:

The hottest year in the past half century was 1998.

OK, I see Wilhelm's point now. IPCC graph does show 1998 as the hottest year since 1850.

n2sooners said:

we have been on a decade long cooling trend.

This conveniently ignores the fact that the past decade has been the hottest in the past 150 years.

n2sooners said:

It was warmer in the 1930s

I see no evidence for this, nor any evidence for your assertion that 1935 was the hottest year in the century. The graph shows an upswing in temperatures in the 1930s, but nothing that is comparable to what happened since the 1970s.

n2sooners said:

And if you want to draw that point that the Earth was warming 150 years ago

No one did that. All I said was that the IPCC showed that temperatures grew over the past 150 years, based on this line from the IPCC report:

IPCC said:

Eleven of the last twelve years (1995-2006) rank among the twelve warmest years in the instrumental record of global surface temperature (since 1850)

Warming in 1995-2006 does NOT equal warming 150 years ago.

(BTW, the industrial revolution is commonly dated BEFORE 1850)