The two boys should have been in school. But 13-year-old Daniel, and his little brother, Kudos, aged 10, were bent double, picking sizeable stones from the soil as their father ploughed the rocky field on which their lives depend.

We were high on the mountain plateau in southern Eritrea. Their field lay at the edge of the little highland village Meshal not far from the border with Ethiopia. It stood in the shelter of a massive outcrop of rock just where the plateau plunged in an awesome sheer drop more than 1,000 feet into a deep ravine below.

The rocks were everywhere. There was not a square foot of soil which did not contain four or five sizeable examples. The larger ones had been removed by the boys, swinging pickaxes into the iron land before the ploughing began.

Their father Gebremariam Goytom was dressed in torn blue trousers and a shirt that had once been white but was now the colour of the land. He had not washed them for two years. A drought had gripped the land for that time. Anyway, as his wife Letenk’iel wryly observed, washing only wore out clothes more quickly.

Gebremariam had risen in the dark. As soon as there was enough light in the sky to warm the muscles of the two oxen he had borrowed for the day he and the boys had set out for the field. Only the oxen had eaten breakfast. They had been given a little of the straw from last year’s unripened harvest, stored in a small stack behind the house, as fodder for such special occasions.

Ploughing was hard work. Often Gebremariam walked at an angle of 45 degrees in order to put the force of his whole body behind the single spiked ploughshare. Behind him his daughter Azmera, 6, poked around in the newly-turned soil for edible wild seeds. Some she popped straight into her mouth but most she collected in the folds of her dress to take back to her mother.

Oxfam’s report that weather-related disasters have more than trebled over the past three decades in some of the world’s poorest countries needs to be seen against the background of the life of people like the Goytoms. For them the problem was drought. But increasing numbers of families suffer from the opposite problem, sudden floods or wild storms. People in such places already live their lives on the edge, teetering daily between survival and starvation. The smallest variations in weather can mean the difference between life and death.

It is easy to speak of natural calamities. But there is nothing natural about the way that a billion people in the world cling in this way to the extremity of existence. There is nothing natural about poor people being on the front-line of climate change. “Poverty, poor governance, patchy investment in the preparation and prevention of disasters; all stack the odds against the most vulnerable,” says Dr Steve Jennings, who wrote the report for Oxfam.

But it is more than that. Being poor means having very little control over your own existence. The decisions which govern the lives of the really poor are made by other people. The moneylender, the employer, the multinational company, the government, foreign governments, the international finance bodies – all often have more say than do the poor themselves. The weather – drought, flood, hurricanes and storms – is just for many the final straw.

As the day progressed, and the sun grew in grilling intensity, Gebremariam and his two sons worked on, taking turns at ploughing and terracing. Man and boys toiled until just before noon when the heat became too much and they returned to the shade of their thick-walled meagre mudhut.

Late in the afternoon the skies darkened and in the distance rain clouds loomed. They lingered for three hours but failed to deliver. As the twilight crept over the little village Gebremariam took one quick glance at the sky, as if a longer look might tempt ill fortune.

“Are you counting the stars?” teased his wife.

“The clouds are right. The winds are right. The ploughing is complete. Perhaps God will send the rain.”

It did not come, though that might have had less to do with any deity than with the gas-guzzling planet-warming lifestyles of an affluent world, several thousand miles away – and quite careless of the impact our decisions have upon people like Gebremariam Goyetem and his children.