Introduction

In the course of climate history over the last millennium, there has been intense interest on the cooling documented to the 19th century for the Northern Hemisphere (NH) at least, the cooler period of climate in the 19th century and rapid global warming during the late 20th century. Over the last millennium climate has varied by as much as 1 °C globally (IPCC, 2001a). Key questions of any future impacts of global warming are the effects on human society and economics, and in particular, on agriculture and forestry. History can provide very valuable lessons on effects of climatic variability on the human dimensions. The multidecadal cooling of the late 16th century in Europe resulted in one of the peak cooling excursions of the so called Little Ice Age epoch of Europe. This example of climate variability provides impacts of a mere 0.5 °C cooling in annual mean temperature on society.

Climatic Change (2005) 70: 9-29

© Springer 2005

Increases were observed in surface global temperatures during the 20th century, and interannual climate variability has been observed in many regions of the globe (Salinger, 1994; Salinger et al., 1997). The 1982/83 and 1997/98 El Niños and the 1991 Mt. Pinatubo volcanic eruption (Salinger et al., 2000) caused considerable variability in the interannual climate of tropical regions in the late 20th century. Recently IPCC (2001a) reported on warming trends, confirmation of continuing climate change based on observations from Arctic and Antarctic sea ice, from later ice appearance days and earlier ice breakup days particularly in European Russia, the Ukraine and Baltic countries. Observations of shrinking mountain glaciers during the 20th century and the increase of permafrost temperatures in many areas occurring provides additional confirmation.

Perhaps of more importance are the implications on agriculture that arise from the multidecadal climate fluctuations. If climatic variability in the order of 0.5 °C can cause such dramatic effects on glaciers, flood events and storm surges, agricultural commodity prices, wine yields and other societal effects as documented for the 16th century, then this poses questions of what are the impacts of the projected increasing climatic variability and change during the 21st century. There is now better understanding of the climate system, and the natural and anthropogenic factors that have caused climate variability and change over the past century, and likely changes in climate and its variability during the 21st century (Salinger, 1994; Salinger etal., 1997,1999; IPCC, 1996,2001a). The latest IPCC projections (IPCC, 2001a) from the entire range of 35 IPCC scenarios place temperature increases in the range of 1.4 to 5.8 °C by the end of the 21st century, with likely increases in heavy rainfall events. The 90% range is 2 to 4.5 °C.

Although agrometeorology provides methods and technologies to allow adaptation of food and fibre production to cope with increasing climate variability and climate change (Salinger et al., 2000) lessons from the past are that the consequences can only be dramatic. An overview of past climate trends over the last millennium is provided as a context to view current climate variability and future trends for providing increasing preparedness of agriculture and forestry to future variability and change. Climate trends during the 21st century from scenarios of human activities are described, together with broadscale implications for agriculture and forestry. The United Nations Framework Convention on Climate Change has clauses on 'Dangerous Climate Change'. This concept will be examined in terms of the ability of agriculture and forestry to adapt to anthropogenic climate change this century.

0 0

Post a comment