Arid climate persists in Northwest China despite warmer, wetter weather

Northwest China has become warmer and wetter, but the change remains too limited to fundamentally alter the region's arid climate or resolve its water shortages, a leading Chinese hydrologist said on Saturday.

Zhang Jianyun, an academician of the Chinese Academy of Engineering and former president of the Nanjing Hydraulic Research Institute, made the remarks at the IWHR Water Science Conference held at the China Institute of Water Resources and Hydropower Research in Beijing.

Zhang said warming in Northwest China is unequivocal. Temperatures have risen amid fluctuations over the past century, with the increase exceeding the global average.

The region has also experienced a general increase in precipitation, but the timing and extent vary geographically. Western parts of Northwest China have seen precipitation increase for about 35 years, while the wetter trend in eastern areas emerged only after 2000.

However, Zhang cautioned against exaggerating the trend or interpreting it as evidence that Northwest China is becoming a warm and humid region. Precipitation in the western part has increased by only about 10 to 20 millimeters per decade, while the region's overall precipitation remains roughly comparable to levels recorded in the 1960s.

"The increase represents a quantitative change and is not sufficient to transform the region's fundamentally cool and arid climate," he said, adding Northwest China is also unlikely to develop a warm and humid climate in the foreseeable future.

Higher temperatures have accelerated the melting of mountain glaciers and snow, contributing to increased water flows and changes in the volume and seasonal distribution of runoff in rivers mainly replenished by meltwater, he said. However, warming has also intensified evaporation, offsetting a considerable share of the benefits brought by increased precipitation.

He called for a scientific and comprehensive understanding of the warming and wetting trend, warning that it should not be used alone as a basis for major long-term water-resource and infrastructure decisions.