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http://physicsworld.com/cws/article/news/41202
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Global warming resulting from slowly changing Earth systems could be up to 50% greater than previously thought, according to research by UK and US scientists. The study reinforces the notion that certain poorly understood systems such as ice sheets or vegetation are integral to accurately predicting future temperatures. It also paints an ever-bleaker outlook for our planet at a critical time when world leaders are gathering for a United Nations conference in Copenhagen to discuss practicable ways of mitigating climate change.
During that period, CO2 values are estimated to have reached 360–440 ppmv (e.g. Raymo et al. 1996) and global mean annual temperatures (MATs) were approximately 3°C higher than today (Chandler et al. 1994; Sloan et al. 1996; Haywood et al. 2000).
Three million years ago, prior to the onset of northern hemisphere glaciation, global mean temperatures may have been as much as 3.5 °C warmer than at present. We present evidence, based on the carbon isotopic composition of marine organic matter, that atmospheric CO2 levels at this time were on average only about 35% higher than the preindustrial value of 280 ppm. We also present carbon isotopic evidence for stronger thermohaline circulation in the Atlantic Ocean during the warmest intervals and propose that the North Atlantic “conveyor belt” may act as a positive feedback to global warming by enhancing sea ice retreat and decreasing high latitude albedo. Based on our results, it seems unlikely that the mid Pliocene warm period was a doubled CO2 world.
We find that while ocean surface temperatures were significantly warmer (6C) than modern temperatures during the early Pliocene, they were also as variable as those during the late Pleistocene, a surprising result in light of the subdued variance of oxygen isotopic time series during the interval of 3–5 Ma.
CO2 is a greenhouse gas that traps heat in the Earth's atmosphere. This leads to a warming effect on the planet, known as the greenhouse effect. As the concentration of CO2 increases, the Earth's temperature also rises, resulting in changes to the planet's climate patterns.
Scientists have found that the Earth's response to increasing levels of CO2 is more complex and severe than previously thought. This is due to the fact that the Earth's climate system has various feedback mechanisms that amplify the effects of CO2, such as melting of polar ice caps and release of methane from permafrost.
The consequences of underestimating Earth's response to CO2 include more frequent and intense extreme weather events, such as heat waves, droughts, and hurricanes. It also contributes to sea level rise, ocean acidification, and loss of biodiversity, which can have significant impacts on human societies and ecosystems.
Scientists use a variety of methods to study Earth's response to CO2, including collecting and analyzing data from ice cores, ocean sediment, and tree rings. They also use computer models to simulate the Earth's climate and predict future changes based on different levels of CO2 emissions.
To mitigate the effects of CO2 on Earth's climate, we need to reduce our greenhouse gas emissions by transitioning to renewable energy sources and implementing more sustainable practices in industries such as transportation and agriculture. Additionally, protecting and restoring natural ecosystems can help absorb and store carbon from the atmosphere, helping to mitigate the impacts of CO2 on the planet.