Source: Global 'cooling': how will the IPCC explain 15-year temperature hiatus? by Sophie Yeo, www.rtcc.org (Responding to Climate change.org), September 25, 2013.
Notes: Climate sceptics love to point out how temperatures have not risen for 15 years. Since 1998, climate change leveled off considerably after a steep upward trend throughout the eighties.
Do scientists have a response? Yes, they do. According to this article:
1. Each of the last three decades (2000s, 1990s & 1980s) is warmer than all preceding decades since 1850, with the first decade of the 21st century topping all the charts.
2. In climate science, trends are observed over centuries, rather than year on year. Thus, the idea that last fifteen years between 1998 and 2012 has been a period of global "cooling" is seen by almost all climate scientists as 'cherry picking the data.'
3. Most scientists argue that taking 1998 as the starting point automatically gives a false conclusion. 1998 was exceptionallly hot, thanks to strong El Nino conditions transferring heat from the oceans to the atmosphere.
"Taking 1998 as the starting year is a joke," says Pieter Tans, a climate scientist who worked on the IPCC report. "Why not 1997 or 1999? Anyone doing this gets an 'F' grade in introductory statistics."
4. The natural variability of the climate can cause considerable fluctuation in global temperatures year on year, in spite of an overall upward trajectory.
Dr. Katharine Hayhoe, a climate scientist at Texas Tech University explains it this way:
"Over relatively short, non-climate timescales (less than 20-30 years), these patterns of natural variability can lead to all kinds of changes in global and regional near-surface air temperature: flat, increasing, or even decreasing trends,"
This short-term variability reflects natural patterns of heat and energy exchange between the different components of the Earth's system. Only over climate timescales (typically, 30 years or more), do the long-term trends emerge that reflect the influence of changes in atmospheric levels of carbon dioxide."
5. It is ocean warming that dominates, while the heating of the atmosphere is relatively small.
"Warming of the ocean accounts for more than 90% of the extra energy stored by Earth between 1971 and 2010; melting ice (including Arctic sea ice, ice sheets, and glaciers) and warming of the continents and atmosphere account for the remainder," according to a leaked 2013 IPCC Fifth Assessment Report.
As environmental scientist and climate blogger Dana Nuccitelli wrote July 2013 on ClimateProgress: "It would be more accurate to say that global surface air warming has slowed, but the overall warming of the Earth's climate has sped up."
Image Source: smswsf.wordpress.com/tag/clown