The Physical and Economic Reasons for Noticeable Warming There a number of reasons to expect at least moderate warming in the 21st and 22nd Centuries. First, as the warmers will tell us (whether we are listening or not) there are increased levels of CO2, methane, and other of global warming agents. More importantly, we are in only the second century of upswing from the end of the Little Ice Age in the late 1800s or early 1900s. The roughly fifteen hundred year cycle moves up on average gradually for six or seven centuries before the shuddering drop, like a roller coaster, into cold weather; therefore, continuation of the natural cycle would be a gradual warming. Possibly most important, there are ongoing industrial revolutions in what were called the Second World and the Third World in the Twentieth Century. The cliché is BRIC (Brazil, Russia, India, and China), but many counties are in a rapidly industrializing phase with economic growth rates of averaging 5% or more each year.